There are lot of moisture sources in inside the apartment. Higher water vapor, capillarity, poor air-tightness, material moisture condition, wood product moisture content could be the reason for higher moisture condition in indoor air. A typical family, due to respiration and perspiration, generate around 20 to 24 pints of water vapor per day which are continuously store inside the room [George. T]. Normally in cold climate, the outdoor air is very dry because cold air hold little water vapor. That times water vapor removed by the dry outdoor air, the infiltration of cold. Normally mechanical ventilation or dehumidification can keep a good inside indoor air quality. However, in summer or spring or humid climate, the outdoor air is almost moist like as indoor air. In such case, infiltration or ventilation are less effective to remove the moisture from the indoor air. Considering the following problems, it is suggested to keep continuous ventilation or dehumidification maybe the proper way to keep a good indoor moisture level. Some time the ventilation efficiency may be the cause of higher moisture level indoor air. When the ventilation system design for 50 ft3/min, and the system just capable only half of the design flow because of outside air, location, system capability etc. than that could be the reason for higher moisture content in indoor air.
6.2 Most common place of mold attack
There are some place where it can easily visible the mold attack. Some are visible and some are invisible. The location are mention below
Invisible location:
Opposite side of wall paper
Roof material over the ceiling
Under the carpet
Those place where pipe passing inside the wall
Building insulation
Vapor barrier
Skirting board
Visible location:
All structural joints and corners
All wall near the ceiling and floor level
Attic
Surrounding the opening
Joint between plumbing material and the wall
Ground floor
As mentioned before that the air-tightness directly responsible for higher energy consumption, poor indoor air quality, higher moisture content and bad human feelings. Actually it is responsible for higher moisture content and this higher relative humidity have an impact on building materials emission, mold growth, comfortless situation etc. Higher moisture may responsible for materials corrosion, decrease the insulation power, damage the envelope etc. If the building is not well airtight there is a chance humid air transfer from the building envelop, also water transfer from ground floor, vapor diffusion into the building material, water passing through the joint or ceiling by gravity force, wind driven rain on the building surface. If the building is too airtight without proper ventilation system than present moisture or moisture source inside the building can increase the higher moisture content or relative humidity. This could be the reason for moisture condensation. There are number of ways to solve the problem such as air-tightness test which help the leakage area and also locate the leakage zone, pressure diagnostics system, polyethylene test for checking the water passing through the ground floor, spray test for finding the moving water into the building envelope, Thermo grapey test for air leakage and surface condensation problem, dew point calculation and so on.
The mentioned six way are directly depend on the building air-tightness. Some have minimum effect or some have maximum effect.
6.3 Relative humidity and mold growth
Absolute humidity or relative humidity always are the main reason for mold growth. Mold decay the building because the resistance power of the structure against mold exceed. as mentioned before that some common part of the building such as the floors, roof, lower part of wall are often exposed to high humidity which provide a good environment to grow up a mold. Material ageing, humidity, temperature, exposing time are quite important factors and among of those factors, humidity is directly related with the building air-tightness. Different research paper already proved that the critical humidity requirement range between 80 to 95%. May be within this condition, the mold growth also depend on the other factors.
Mold growth also depend on the material structure as well as material property. Mould index also different for different materials. VTT building and transport have been studied for long time and found that the ambient RH 80% to 95% could be the reason for mold growth but sometimes it also depend on the other factors like temperature, exposure time, material moisture content.
As mentioned before that VTT already develop a mold growth index[Viitanen, 1997]. The VTT's mold model based on the mathematical relations for growth of mold where some other factors also have an influence. in this figure 6.3.1, different type of building materials such as wood, gypsum board, mineral wall, fiber board were investigated. Wood material shows higher mould index within very short expose time. It is well known that Nordic countries people use higher amount of wood product as a building material as well as decoration material. So those countries are always show us the critical condition for growth of organism. So if the buildings are not well air tight or the building are proper airtight having no proper ventilation system than there are much more possibilities to build up a proper environment for the mold growth. In the fig 6.3.2 mold growth falling down a huge percentage with slight change of RH value. Wood
product show us the maximum index 4 after 37 week and gypsum board are quite save and showing the minimum index value. This two graph can be summarized that the emission from material or mould growth on building material surface directly depend on the relative humidity. RH˃ 95% and temperature +20° to +40° are always consider as a critical condition for the wood based materials. Sometime lower temperature and maximum higher relative humidity don't have any effect if other factor are stay quite normal. In fig 6.3.3, different temperature were consider with different relative humidity.
At +5°C with maximum RH 100%, mould index of the material was high but at least 84 days later. But At +20°C with maximum RH 100%, mould index of the material was reach the higher condition within the 28 days. It can be conclude that moisture content, relative humidity, temperature and duration of the exposure are the main factors which are responsible for the mold growth. Normally at winter and summer the inside room temperature are around 21 to 24° for Finnish building. So it is not possible to control the mold growth through the temperature and time of exposure also not possible to control. The remaining two are moisture content of the material and the relative humidity inside the building. Moisture content of the materials can be control by selecting the M1 categorized product but to give a solution for the relative humidity than there is a no way except an airtight building with balance ventilation.
6.4 Characteristic of moisture damage in indoor air
Higher moisture content in indoor air always show the bad impact on the building structure. This may lead to physical, biological and chemical contaminates in the indoor air. Higher moisture content in Indoor air means the capability of hold extra moisture are going down. Building air-tightness, joint defect, crack, poor ventilation system, building material moisture (inside), kitchen, toilet, leaky plumbing system etc. may cause the higher moisture content in indoor air. Those things are directly responsible for condensation and this condensation cause the building dampness and this dampness is a suitable place for microbial growth. Such type of structural damage and biological and chemical contamination could be the reason for poor indoor air quality and it show a serious risk to the performance of building structure [ Oliver A, 1997].
Characteristic of moisture damage can be estimated in different ways but usually the most effective way is observation. The observation can be done by building inspector, owner or any special person. There are many sign to find out the moisture damage in building materials such as materials color, peeling, window panes, building shrinkage, blistering, materials decays etc. The most common damage place are building corners, ceiling, wall surface near ground floor, window frame, toilet, kitchen etc. It is always advisable to make a report about the building dampness or moisture condition by a expert inspectors. From two Finnish study, advised to consider the damage location characteristics, damage duration, type of damage observation (such as mould, odour), and characteristics of damaged material [Pekkanen et al, 2007 & Haverinen et al 2003].
6.5 Moisture impact on indoor air
It is very common for the cold climate country's buildings to transfer heat, moisture, air through the building envelop which can responsible for higher moisture content in indoor air, building materials, condensation which are direct threat for the product's durability, functionality, mould growth, poor indoor air quality etc. Generally, microbes may grow at any surface where the minimum moisture and nutrients are available for their growth. In Finland, the mean temperature at February vary from -6° to -14°. The average temperature in summer is 13-17° and the annual precipitation less than the 650 mm [Karisto, 1997]. Normally indoor air humidity are always low in cold season because of less moisture content in outdoor air. Through lower humidity never minimize the moisture problem in indoor air. If the building is not properly airtight that there are a chance of water leakage from the building roof, walls, windows, balconies, foundation. Frost can also increase the size of crack. Wall cavities can responsible for mould growth [Lawton et al, 1998 &Flannigan et al, 1996]. Interior plumbing leaks, , faulty washing machine, shower room, kitchen also responsible for the moisture problem in indoor air. Sometime building materials contain huge moisture which could be the curtail factor for moisture growth [Haverinen et al, 1999]
With considering the following factor, a grading system was induce to show the moisture damage in dwelling. The grading system classified into three part. Grade 1 characterized as absence of visible moisture damage. Samples with notable moisture content are classified as grade 2 and Grade 3 having a significant moisture problem [Nevalainen et al. 1998]. Grade 2 and 3 showing the maximum moisture problem that why it is called as index homes and Grade 1 homes called as reference home. Around 630 Finnish building and apartments were chosen from three large city in different region. Three region were chosen based on different temperature. The building were made between 1950 to 1989 in Oulu, Kuopio and Helsinki. 54% of house are taken from Kuopio and rest of them were taken equally from other region. The sample apartment were taken equally from the three different region. The observe value taken by the civil engineer where the guidelines (walls, roofs, floor, windows, ventilation, plumbing system) were specified clearly. Temperature and humidity also recorded for both inside and outside of the buildings.
The home space condition divided into three part such as bathroom, kitchen, other space. These three part were added into the domain. The damage of every domain also tagged with the surface or the equipment. Interior material details also included the domain. all information coded carefully and processed using the SAS statistical software. There was a standard predesigned checklist scale where every damage scaled very clearly [Nevalainen et al. 1998]. The mean number of damage sites for grade 1 was 0.28 for both houses and apartment. For grade 2, the mean number of damage site for house and apartment were 1.4 & 1.7 and for the grade 3, it was 2.4 & 2.6 respectively [Chelelgo et al, 2001]. Through the domain system it was possible the moisture distribution at different space. Table 6.5.1 shows us the moisture distribution in different location and space.
Grade 3 shows the maximum percentage of moisture damage in every locations. The result show us the maximum damage occur in (both type of dwelling) in Bathroom. Bathroom also the key place of having maximum moisture damage for every grade and dwelling. It could be the reason water vapour after shower, water leakage, building materials poor ventilation. The other place such as rooms, bedroom, basement, etc also showing the much more damage sigh in apartment compare with house. The index apartment shows more damage than the index of house. It does not mean that the room house gave better moisture condition than apartment. The index of apartment high, could be the reason of less caring of moisture damage. Other cause could be the building materials which use in the apartments. May be those building materials much more suitable than the wood materials which were used most of the house. The other place of apartment showed only 21% moisture damage and 14 % moisture damage for the home. The measurement of relative humidity also taken which showed that around 85% of house and 60% of apartments had a RH between 20 - 45%. 20% of homes having RH more than the 45% [ Chelelgo et al, 2001] Keeping a good RH condition may be the reason of external wall of the apartment. Around 85% of apartment's external wall were made by concrete and 90% of house were a timber structure [ Chelelgo et al, 2001]. This two type of structure always shows the good resistance power against cold climate.
6.6 Case study
Building Description:
Two storey single family house located in Tapanila. It is also named as Tapanila ecological house.
Moisture always attack near the ground floor and near the ceiling. That why MC were measured near the 200 mm from the floor and ceiling. 32 moisture pins were installed as well as temperature sensor.
Air-tightness data:
The building was carefully measured the air- tightness data. The data were collected for one bed room and the full house. Depressurization system was used because of lower
indoor pressure than outdoor. The measured result was 3.1 ach at 50 Pa. According to the classification of Laine and Saari (1998) about Finnish house air-tightness standard, good house refer as (1-2 ACH), normal house (3-4 ACH) and leaky (˃ 5 ACH). According to classification the house is classified as normal house.
This shows that the air-tightness of the house is quite good, especially considering its somewhat complicated structure. The surface leakage rate for test room and house were respectively 0.5 and 1.1 L/(s m2).
Indoor humidity:
As mentioned before that the indoor humidity depends on outdoor humidity, temperature, human behavior, ventilation rate, building material moisture content etc. This is single family house with 2 adult and 3 children. In the building description table 6.6.1 the ventilation rate as well as temperature are well defined. The average indoor temperature in winter and summer including the standard deviation were 21.4 ± 0.5° C
and 23.4 ± 1.1° C. The average indoor relative humidity in winter and summer including the standard deviation were 21% ± 3% and 30% ± 7%. The absolute humidity in winter indoor air around 1.9 g/m3 higher than the outdoor absolute humidity (0.7 g/m3). In summer the absolute humidity for both season are almost same. The fluctuation of humidity difference were much more higher in winter and these value is
almost (2-4 g/m3) [Tolstoy, 1993 & Rodriguez et al. 2000]. Moisture pin gave the
The value was taken in April' 98, October' 98, June' 99. and these figure 6.6.2 also show the heating system impact. The initial moisture of the building wall need time to dry and when heating system were operated the moisture content going down for interior wall and roof envelope. It reached the safe condition below the mold threshold level(80% RH, 0.16% kg/kg, 15°C). Before occupation of people the Umax value going down less than 0.1% kg/kg.
In another case study, the temperature and relative humidity were measured in bedroom, living room and outdoor. For that, 101 lightweight timber detached house were tested in Finland. The data were collected one hour interval over a one year period. Different type of data range were found because of different envelope structure, heating and ventilation system. As mentioned before that indoor temperature and humidity are important factors for human comfort so it is very sensible to design a temperature and humidity for comfort indoor air condition.
Around 101 lightweight timber house were measured and all were single family house. The design details and the materials property collected from the manufactured company. The house had three different type of ventilation system such as passive ventilation, mechanical exhaust, mechanical supply and exhaust ventilation system. The measured period was between July, 02 to June' 04. Average floor area and volume were respectively 153 m2 and 386 m3. The envelope leakage rate (at 50 Pa) was 4.0 m3/ (h.m2) and air-tightness 3.9 1/h. The ventilation rate was 0.38 ach. The occupancy area per person was 43 m2 [Kalamees et al, 2007]. From FiSIAQ (2001), it was given a target value of temperature and relative humidity at different season for different category.
Two summer season were considered one was 01.07.2002 to 10.09.2002 and another
was 04.07.2003 to 25.08.2003. The average outdoor temperature for the both summer was 19°C. The winter season was consider from beginning of December to the end of February. The average outdoor temperature for two conjugative year were - 8°C (minimum - 29°C) and -4°C ( minimum - 22°C). For summer , the average temperature and humidity were respectively + 24.8°.
(range between +22.2° C to + 28.5°C) and 51% (range between 34% to 60%). 19% of room (first summer) and 2% (second summer) of room remained below the limit of S2 category [Kalamees et al, 2007]. 53% (summer 1), and 63% (summer 2) of room were fulfilled the thermal requirement for S3 category. For winter , the average temperature and humidity were respectively + 21.6° (range between +16.9° C to + 26.5°C) and 26% (range between 14% to 47%). 2% (winter 1), and 4% (winter 2) of room were fulfilled the thermal requirement for S3 category [Kalamees et al, 2007]. The average humidity in summer was 11.5 g/m3 and 5.0 g/m3 in winter. Comparing the both season the summer time gave higher result of actual humidity compare to winter season and the average of summer was 2 time higher than the winter time. It was because of the summer time the indoor & outdoor temperate was high which means the air were less capable to hold more humidity. These problem increase the chance on condensation and provide a mold grow environment.
6.7 Some investigation and respective reason all over the world
Moisture problem can occur inside the interior wall, exterior wall, inside the exterior wall. Moisture are always present in the inside building but the poor indoor air quality occur when it cross the limit. Normally moisture refer the situation when it cross the higher limit to create a problem. Excess moisture content in indoor air is the main reason of biological contamination. The effective condition for the moisture growth are RH˃80% [IEA, 1990]. The movement of moisture could be reason of poor insulation,
less airtight or vapor barrier. If the building is not proper airtight such as having basement leakage, foundation drainage, poor joint problem than moisture problem are usually occur inside the building. To support the above statement, this paper also give some case study result.
A survey was made around 334 "Lowa" households during 1988 to give a baseline data about energy efficiency, moisture effect and other relative data. the most common moisture problem were found in windows condensation, paint peeling, mildew on inside envelope. This survey also found that moisture problems occur most of the energy efficient building [Prestemon, 1991].
During the 1979- 1980 winter, the Portland study surveyed around 103 older homes and the study found that the average relative humidity and temperature were 56% and 20°C which could be higher in the milder fall and spring. 46% of the room had bathroom exhaust fan, 91% used thermostat at night, air-tightness 16.2 ACH at 50 Pa. The result was found that the room's contain higher moisture content air and around 73% room had the condensation problem [TenWolde et al, 1986].
In 1984, "the Lane Country Housing Authority Study" was investigate six rental resident houses where many unit of exhaust fan in bathroom, kitchen were not working and some were very noisy. That's why the resident prefer to off that most of the time. 67% mold or mildew was observed in three apartment out of six. The indoor relative humidity were so high than the acceptance limit [Tsongas, 1984].
The large group, "Tri State Homes" manufacturing homes more than 5000 from 1970 to 1987 and when they made an investigation on those building, they found all of homes
have moisture problem. Those homes were very airtight and poorly ventilated. This lead to higher indoor air humidity. Moisture problem occur because of poor ventilation and higher moisture penetration [Merrill et al. 1989, Tsongas, 1979, Tsongas, 1985]. Another common problem find in attic because of cold water vapor always try to move up and condense in the cold part of the attic. Thus could be the reason of mold growth and structure damage. Attic condensation occur due to the leak in the ceiling and pressure difference in room. The survey found that the most common moisture damage occur in the window frame, corner of joint, attics, bedrooms, closets. The decay of window was caused by leakage of shower water into the wall cavity. The survey was conclude the following reason such as stove top boiling, wood product, shower, leaky basement, poor ventilation system, poor efficiency of mechanical ventilation and design etc. the survey recommended to improve the ventilation system, solving the attic problems, reduce moisture generation, draft proofing, better air circulation, renovation of old home (20-30 years).
In Seattle, Washington, around 72 unit of apartment were investigate and found the mold and mildew on wall and carpet. The experts blamed the poor wall vapor barrier, wall leaks that allow rain water to enter the walls, cellulose wall insulation, leaky foundation. The water leaks were occur because of poor sealing materials were used in outside and wetly basements because of capillary action of the water. The other problem was poor circulation of air which gave a higher relative humidity condition inside the indoor apartment [George. T].
In another case study by Portland, in Oregon found the mold, mildew, window condensation in an older apartment. The mold found at the ceiling near the exterior wall. The building was well airtight (concrete block wall) building, insulated (even the ceiling), good sealing material used. But the main problem, there was no kitchen and bathroom exhaust fan as well as small in size and the volume. The expert summarized the reason that the insulation of ceiling was not extended to the outer edge of the ceilings kept the ceiling surface cold, having the higher relative humidity. This led to grow mold at the ceiling near the exterior wall. To consider the energy consumption house or low energy house, it is recommended to make the building as much as airtight and well ventilated to save the money and energy from space heating part. In low income housing occupant always prefer not to use mechanical ventilation system and save the money. Thus could be the reason of poor indoor air.
Florida air conditioning system also investigate the ductwork of hundreds of air conditioned homes in Florida and found that the leaky ducts which had an effect on the energy consumption and moisture content. Those leaky ducts cause poor air condition and keep more humid which lead to moisture problems. The experts were suggested to seal the ductwork.
The Northwest Wall moisture study 86 newly constructed homes in USA. All the homes had age between few months to three years old. 50 homes were selected from metropolitan Seattle - Olympia area, 16 from rainy Washington coast, 20 from cold Montana region. 73 out of 86 had an air to air heat exchanger and rest of them having humidifier. Some of them air-tightness measure through blower door and rest of them measure Lawrence Berkeley Laboratory methodology [ASHBAE, 1989]. Different type of ventilation system such as spot exhaust fan, air to air heat exchanger were used. But those were not properly functioned. One third of house were not use air to air heat exchanger, two third of house didn't have kitchen's ventilation and half of them didn't have the bathroom ventilation. All those ventilation system didn't have enough capacity to remove of extra moisture. Different type of moisture problem were observed in those house such as mold growth, high relative humidity, window condensation, dampness of wall and ceiling. The expert were suggest to improve moisture condition through better ventilation, dehumidification, airtight construction [Tsongas, 1990].
In another case study, found the cause of existing roof moisture damage in flat roofed building near Medford, Oregon [Tsongas, 1986]. It was made early 1970s and the inner part was used plywood, insulation, a thin rubber membrane covering the outer plywood surface. The expert found that the water dripping ceiling, ice damage, condensation of water vapor which were the main reason of structural damage inside the building. Because of poorly airtight building, there were lot of leaky space which were the reason to keep a cold surroundings and highly wood moisture content.
Most of the moisture problem in indoor air are directly related with the indoor relative humidity which is caused by poor air-tightness, proper ventilation and poor building design. In mild weather, ventilation system is not working properly. Installation of dehumidifier could be the best solution for such type of weather. Proper air-tightness, selecting M1 category materials, spot ventilation, balance ventilation could be minimize the inside relative humidity which can protect our indoor environment against mold growth and minimize the other pollutant concentration.
6.8 Case study 5 building
Building 1
Description:
Four storied wood framed building, age of four years, having a highly insulate, air-tightness property and double or triple glazing facility. Each suit had natural gas vent furnace and ductwork physically situated at the corner between exterior wall and the ceiling. Mechanical humidification was seldom used.
Symptoms:
Moisture problem, moisture leaking out of the wall in winter time, having more effect on corner suites, wetting effect occur short spell in winter.
Analysis the symptom:
The leaks were found at the above of the window and cracks had increase the dimension during the winter. First of all the building was not properly airtight. secondly the materials were very porous as well as the joint too. That why when the water come through the leaks, it was going down through the porous material or joint by gravity action deposition over the window. So the wall between leaky area to deposition place were showing dampness. In winter, some spell of days, temperature were high compare than the average temperature. first, through the leakage the water were seepage, than frost which increase the dimension of crack, than again melt and passing to the downside by gravity action. If such type of problem occur, that means the air-tightness property of the buildings are going fall. So air leakage through the building envelop can increase the moisture content of building material as well as increase the air relative humidity which can increase the coldest part of the building. as mentioned before that this coldest part are responsible for mold growth and higher relative humidity increase the building's material emission. The reason of more impact of corner suits because of the placement of ductwork. It was placed in exterior wall and ceiling corner. Normally the hidden joint are more leaky. That could be the reason for the corner suit. The corner suits had much more exterior envelope compare to other suits. So wind driven rain and surface condensation could be the reason.
Solution:
Sealing the hidden joint behind the ductwork. Provide minimum pressure difference all around the building. Pressure relief grilles are recommended to install in the bulkheads of each suits.
Building 2
Description:
Three storied building, age of thirty years, having a interior strapping and moderate insulation system and flat roof with big crawl space in foundation. The heating system consist of gas fired boiler and base board heater. Self control mechanical ventilation system in bathroom and the top of the roof. No mechanical humidification were used.
Symptoms:
One of the suits have high relative humidity among the other suit, roof leakage.
Analysis the symptom:
Roof leakage was the main problem. After changing the total roof structure and check the building air-tightness and it satisfied the recommended value of air-tightness. Again problem occur one suits at the top floor. The investigation found the reason and it was crawl space. But the arrive question was, why not the other suits were effected of ground floor and first floor. Actually there was a plumbing chase connection was used between crawl space ant the top floor's suit. and the pressure difference between the crawl space and the top suits was 11 pa when the blower door was operated. this plumbing chase didn't have any opening on other floor. The water vapor at crawl space was passing through the plumbing chase and came out at the top suit. as mentioned before the roof was poor insulated and condensation were occur easily. So crawl space could be the reason for condensation.
Solution:
Good ventilation system in crawl space can reduce the pressure difference between crawl space and upper floor. Improve the building air-tightness by sealing all type of gap. Ceiling always the warmer part, so try to make ensure no seepage and deposition of water. Secondly to provide a water tight ground floor surface and sealing properly all type of connection (plumbing, electrical) between crawl space and upper floor. Thirdly, sealing properly the entrance and existence face of the plumbing chase.
Building 3
Description:
Three storied building, age of eight years masonry structure. Foundation part consist of big crawl space, piles and grade beams and truss used as a roof structure. The heating system control by central heating plants. Corridor pressurization system and individual exhaust fan were used as a mechanical ventilation system.
Symptoms:
Wet spots on the ceiling, wet area found in west side of the building.
Analysis the symptom:
All the plumbing pipes were passing through the west side and the inspection team thought the leakage of plumbing unit. But no leakage was found. There were some observation about the building such as the building placed in open area with nominal vegetation, secondly the water from the roof damped adjacent to the building which increased the water level. A polythene test was done over the ground floor and found huge moisture on the ground floor surface. Thus was the reason of capillarity and higher ground water level. Pressure difference between the crawl space and the upper floor are around 8 Pa that could be other reason. So if the ground floor are cover by the carpet or PVC than there are a huge chance for mold growth and building material emission. The huge moisture content of the ground floor transfer to the nearby wall. Than huge amount of emission occur from the wall paint. This higher content of moisture assist the mold growth, increase the material emission and responsible for poor indoor air quality.
Solution:
It is possible to solve this problem by providing good ventilation system in crawl space. Secondly to provide a water tight ground floor surface and sealing properly all type of connection (plumbing, electrical) between crawl space and upper floor, check the ground level water level, select a moderate type of filler (mix of coarse and fine aggregate) and keep a distance between dumping water zone and building foundation.
Building 4
Description:
Six storied building, age of forty years old building. The moisture problem were occur in its wall system. The wall structure was combined with brick veneer, concrete blocks, wood strapping, insulation, polyethylene vapor barrier and drywall. All windows are double glazed, wood frame with aluminum horizontal sliders.
Symptoms:
Moisture related problem such as blemishes, bulking dry wall, mould growth near the floor (1 feet above), near the window, electrical outlet.
Analysis the symptom:
From the symptom, it can easily identified the reason and the reason was air leakage because the window part were most effected part. Most damage occur in 4th 5th and 6th building. So here had no chance to grow a moisture 1 feet above the floor level. The reason could be the pressure difference of each floor or the pressure difference exterior wall to interior part of the building. Due to different pressure difference, air ex-filtration could be play an important rule. From the tenants response that they had changed the window for the upper floor but still the problem were same. Investigation found the problem in the window and air leakage. Air leakage through the window in winter and ex-filtration air get condense and frost into ice between two panel of glass. In spring or other time when the frost going melted there was flooding occur. Most of the time the window frame or sill are responsible to drain out the water but this window sill collected the moisture. The water stability on the sill gave permission to move wooden frame. The other cause could be the shrinkage problem which give ample pathway to move the water into the frame.
Solution:
At first, it is recommended to select a window which are shrinkage free. The sill of the window should be mentioned a slope. Drain out point should be logged free. The two glass panel should be kept 100% airtight so there are no chance to condense the ex-filtration air. The frame fixed with the wall should be air tight and at the bottom of the frame or the intersection surface between window and the wall should be kept moisture barrier layer. Water proof coating on the frame and sill could be bring a good result.
Building 5
Description:
Single story wood frame house, constructed time in 2001. Its foundation were higher out of the ground level compare the other nearest house. The house had concrete foundation with insulation, vapor barrier, damp proofing. The floor slab was concrete slab and rest on the granular fill.
Symptoms:
Wet spot on the wall, behind the insulation materials
Analysis the symptom:
A serious of text occur and also tested the soil under the foundation as well as the surrounding of the house as well as the water level. From the investigation, it was found that the house was sitting on the silt layer and this silt layer rested on the clay. Silt is quite permeable but clay is comparatively less permeable So when water was passing through the silt layer than it was halted in clay layer and made a water bowl between these two layer and from this layer water was penetrate into the foundation by capillary action which reached the ground level.
Solution:
Actually this example is not part of air-tightness impact on poor indoor air. Lot of works have already done on building air-tightness in Finland and give a solutions. But some problem still are same. Structural problem, design problem with combined air-tightness and proper ventilation can solve those problem. It was recommended to install a capillary break under the footing for the existing building. Increase drainage system could be assisted to improve the condition. Polyethene moisture barrier on the basement wall was another solution to protect the wall.
7.0 Controlling and improving
7.1 Improving building materials emission
There are two ways to keep a good indoor air quality. First of all material selection and proper ventilation. Proper building structure design also another way to minimize the intensity of this problem. There are some following steps that are recommendation to keep a good indoor air quality.
Test the material emission. It is always recommended to select low emission materials as a building material. Finnish standard can be use because around 250 building materials are tested and categorized very clearly while considering the other important factor.
Moisture content of the materials. it is highly recommended to reduce the inside moisture content before use as a building materials. In FiSIAQ, they are recommended to ventilate the room before occupation as well as dry out the material at respective limit. Because at the beginning time the emission rate are so high. So if ventilation period are taken at least 2 weeks before occupancy than it will reduce the moisture content and emission rate of the materials.
Try to use such type of material which briefly description are known such as emission class data, usage limitation criteria, environmental factors criteria etc. Basically the materials should be environment friendly at any situation.
Cleaning should be more flexible easy to reach all over the place. Vent should be duct free, corner, attic etc have to be give extra effort. Cleaning material should be pollutant free.
All the building materials should me more durable. Highly durability shows higher resistance against mold growth. Extra caring should be taken especially for wood product.
Sandwich panel should be airtight and moisture free. proper workmanship could bring the best solution.
Uncoated brick, glass, ceramic tiles may be used freely.
From FiSIAQ, Finnish classified M2 type materials should not be used more than 20% of area.
Recycled material and bio-based material should be give preference
Low maintenance materials always give preference
Low embodied material should be selected because low embodied materials have minimum evaporation and diffusion property
Materials should be toxic free
Material should be recycled, reused and biodegradable.
7.2 Improving the building air-tightness
To improve the building air-.tightness, it is recommended to installing the continuous air resistant layer all around the building envelope including ground floor, joint between the floor and roof with the external wall, sealing all connection from inside to outside or vice versa, windows, external doors etc.
Sealing
Make sure there are no gap between skirting at floor level if there are any gap than sealing could be solved the problem
Sealing the joint between pipes and external wall (which comes from outside) or roof
Sealing around external door and window.
Sealing the intermediate concrete floor joist and later tape joist well with the wall
make sure the air barrier is carried from external wall to the ground floor slab. Than air-tightness sealant could be used to seal the barrier and plaster.
There are also a chance to shrinkage. so during the construction time is recommended to keep this thing in mind.
Recommended to use concrete floor slab because is very airtight.
Try to use a thicker nylon before the
ground slab installing or casting. Ensure the good drainage system under the ground
floor.
Water proofing foundation
Improving the masonry wall
Plaster the interior part
All type of inner joint should be sealed well
Using good quality of plaster material
Crack on plaster could be minimize by proper curing and proper sealing the cracks.
Use a airtight membrane.
Weep hole always block free
Improving the air tightness at window and door:
Make sure the connection are fully airtight
The air barrier have to continue inside the frame back surface and sealed all interfaces between this barrier and frame
Water should not be stay at the lower part of window frame
Wipe away moisture from all type of frame
Installing a weather seal between the (door and window) frame and opening
Improving the attic:
Check the leaks of the attic part because it is one of the colder part of the building and without proper air-tighten it could be the right place for the mold growth.
Check the joint of attic. Shrinkage impact can allow to penetrate water inside and going frost which increase the size of cracks.
Installing the air barrier at the attic and over the whole ceiling.
Ensure proper drainage of water.
Protection against seasonal flooding.
7.3 Controlling the mold and condensation
As mentioned before that the airtight building have more chances to mould growth. But it is possible to control the condensation and mould in airtight building. The four main ways to control those
Ventilation
Insulation
Heating
Removal
Ventilation:
Opening window, door at maximum time in summer and fall of winter.
Introduce the ventilation system at attic, basement and crawl space
Balanced ventilation could be the proper selection among the other and try to control the pressure difference around the wall surface
Install the spot ventilation or automatic exhaust fan in bathroom and kitchen which should have the ability to keep the moisture in minimum level.
Installing ventilation over some moisture producing product such as dryers, stoves, kerosene heaters etc.
Vent and air ducts could be clogged free
Installation of dehumidifier.
Heating:
Maintaining low and constant heat when the weather is so cold or wet. Continuous heating always prefer than the short bursts.
Installing heat globes in bathroom
Insulation:
Installation a vapor insulation in all the building envelope
Insulate the water pipes which bring inside the wall
Installation insulation in attic, corner joint, ceiling, inner side of the exterior wall
Insulated materials should be emission free
Removal:
Eradicate mould is hard to remove.
Brush of those area is not the proper way to solve the problem which could release the spores.
Bleach is not the proper solution, it has higher PH which could be made ineffective to kill the mould.
Use 80% white fermented vinegar solution
Tea tree oil is effective
Other:
Allow sunlight into the room as much as can.
Proper installation of HVAC equipments for maximum efficiency and safety.
Tobacco smoke should be prohibited insider the room
Leaky plumbing as soon as possible removed
Leaky toilet, water sink, kitchen sinks should be sealed well or replaced
All type of buckling board should be replaced
Clothes and shoes must be properly dried
Carpet should be clean and maintenance in at regular basis
Water damaged carpet should be removed or dry it well
Ensure plenty of ventilation in wardrobes
Always prefer to use treated wood
Installing the sky light in dark place
7.4 Way to control inside moisture
1. Turn on the exhaust fan:
In cold climate, air is naturally living the space through the top of the building and enter the building through the base of the building. Between this two there are also a region which called the neutral plane. This plane is called a pressure free plane. The indoor air moved out to the outdoor air because of the higher pressure in indoor. On the other hand, outdoor air come into the indoor air because lower indoor pressure at the base. If there are no wind and building opening are evenly distributed, that means the neutral plane stay at the middle. If a ventilation fan operate that time and there are no wind than total air flow out of the building is the sum of air exhaust through the mechanical ventilation and natural ex-filtration. This must be equal to the total airflow come into the building. So more infiltration means the neutral level are going up so ex-filtration was falling down. So, when the fan is on than some ex-filtration air exhausted through the mechanical exhausted which increase the ventilation and greater than the measured airflow through the fan [Palmiter, ].
2. Dehumidification:
This could be a another important strategy especially in mild and humid condition. It is possible to keep the relative humidity under 50%. It is quite wise decision to choose large capacity dehumidifier to keep a good indoor air relative humidity.
3. Ventilation of crawl space:
Different building code agencies suggest the crawl space ventilation system because it remove the extra moisture from the crawl space otherwise it show an impact on the basement floor.
8.0 Discussion
Lot of reason are responsible for poor indoor air quality. This paper summarized two important reasons such as building material's emission in indoor air and building air-tightness. This paper briefly discussed the different type of emission from individual material, intensity of pollutant from material, influencing factor, some case study and compare the emission from the Finnish building M1 categorized materials with conventional building materials used in building. At the second part, the paper discussed about the current air-tightness condition of Finnish building stock and showed the connection between building air-tightness property with mold growth. At the end, there are some suggestion and recommendation for the better indoor air condition.
The emission of building material and the concentration of indoor pollutant inside the room vary from season to season. Normally in summer higher humidity found and higher humidity is the key reason to condensation, increase the material emission. all type of building materials increased their emission rate. Floor varnish increase around four time more emission if the room humidity change from 30% to 70% wall paint increase around six time more emission within the same condition. The study shows the maximum emission of all type of building material at higher humidity and higher temperature. The case study of temperature and humidity on building material shows the result. The other thing is temperature, increasing the room temperature means that the indoor air contain more moisture inside the air and PVC material shows the real difference. 5°C increase the temperature, shows double material emission rate from PVC materials. The impact of humidity and temperature are not same for every material. Floor covering and PVC shows higher emission at higher temperature where as floor varnish, adhesive, wall paint shows higher emission at higher humidity level. For PVC materials and the sealant, sensory index cross the limit because of higher temperature and Humidity. This special VOCs such as Toluene, n-butyl acetate, ethyl benzene and m,p-xylene equilibrium concentration decreased respectively 32 - 47%, 32 - 33%, 38 - 43%, 46 - 59% when air exchange rate increase from 1/h to 2/h. Having a higher RH impact could be possible to reduce the inside indoor pollutant through increase the building air exchange rate (ACH). But the main problem, it may be cross the limit which is specified for low energy building. Exposure time of building material shows the emission difference during the first year. This paper shows some real building data and true analysis where a huge amount of emission observed at the beginning time compare with the rest of lifetime. Same material but using for different purpose could be the reason of higher emission. The emission from the ceiling materials is much more higher than the floor materials. Manufacture before product always shows minimum amount of VOCs and other pollutant emission compare with the onsite casting. The reason was that manufacture before product get always extra time for proper ventilation of the product. Even M1 categorized materials are recommended to ventilated at least one week before the occupancy. Air velocity always increase the evaporation and diffusion coefficient. Increase the temperature means increase the diffusion coefficient. At the beginning of the product increase air velocity brings a good result and during the exposure time it, the pollutant concentration inside the materials are going down.
The surface emission rate of different floor materials were discussed in previous section where PVC shown the higher amount compare with Linoleum, rubber, polyolefine. At the first day of installation, the surface emission rate almost 2.5 time more compare with after 28 days emission rate. After 28 days, some PVC material shows more than 1mg/m2/h which is not satisfied the S1 class. Comparing the different type of carpet, carpet which made of woven natural fiber with embossed SB foam as a backing material, shown higher emission rate. Normally flooring material is the combination of different type of material. So emission is not only depend on the floor material but also depend on the other combined material. Most materials use plasticizers, surface treating, anti oxidation agent, color, surface treatment agent (varnishes, oils, waxes) things. The prefabricated also combined different wood by glues. Additive (anti-oxidation, stabilizer) are technical things which also the possible source of emission. On site construction process, leveling agent and use of curing injection resin also responsible for emission. Flooring materials with high sink effects absorb pollutant such as tobacco smock from the air and when it is saturated, that it will reemitted those pollutant as well as oxidation product too. The floor concrete might be wet or damp through leakage of pipeline and this is responsible for hydrolytic decomposition reaction as well as degradation product. Casein is commonly use in building material which are coming to touch with moist surface than it emitted ammonia, amines, sulfur, alcohols. So when relative humidity is high there is a possibilities to emit formaldehyde, hydrolysis, decomposition reaction, degradation, monomer emission etc. But the complete structure always show us the minimum emission than the summation of individual product emission. This may be the reason of absorption, neutralization of inside action or proper sealing of the material. Carpet installation adhesive emitted much more pollutant than the carpet themselves. [Sheldon et al, 1988]. emission from the adhesive at the beginning, were so high. 1,2 propanediol, TVOC emitted respectively 3459 and 2990 µg/m2.h. But after 29 days later all the component reached in S1 level. German association for the control of product emission for flooring installation tested different type of adhesive and summarized the key pollutant with maximum emission rate. This paper also discussed the real case and found the emission from the combined materials much more lower than the summation of emission from the individual material. It's may be the reason of sorption impact and different permeability of flooring materials, the chemical reaction may neutralize the alkaline emission, proper sealing could be the another cause for reduction emission. When two or more individual component working as a composite component that the expose material area going decrease which could be the reason. Water based latex paint more used in the interior paint which contain organic solvent.1,2 - Propylene glycol was the common pollutant for all WBP. The emission at the beginning time were so high but within 14 days it were going down into limit. It's because of sorption and diffusion properties. Solvent based coating shows 840000 µgm-2h-1within the 8 hour which reduce to 1400 µgm-2h-1within 14 days. The emission rate were so high from first few hour and it was the drying time of paint and at that moment most emitted pollutant were aromatic and alkenes. Natural paint having aromaticized petroleum solvent which is responsible for aromatic pollutant emission. Natural water based paint release ammonia into the air during its application on the surface.
The case study shows different building material used as a floor covering. PVC shows higher TVOC after 12 months. The mean value was 117 µg.m-2 h-1where as when parquet use as a floor covering, the mean value was 28 µg.m-2 h-1. Ceiling material shows higher TVOC emission range 26-260 µg.m-2 h-1 among the different part of the building such as floor covering, Ceiling, Walls. Ammonia and formaldehyde also shown higher emission rate from ceiling material. Sometimes the range didn't fulfill the S1 level requirement. The case study also found the difference between measured and calculated value of TVOC, Ammonia, Formaldehyde which indicate of presence of other pollutant sources. But in the laboratory the emission was available for a fixed temperature and humidity (constant and it was 50%.) but in real there was some variation (humidity 15-74%) in both factors. Possible sources could be the kitchen furniture, window frame, skirting etc. Single VOC, VOC group and SVOC could be the reason for the difference of measured and calculated value. Same material, PVC, were used as a floor covering, ceiling and walls. The contribution of TVOC were 34% from the floor covering, 37% from the ceiling and 41% from the walls after 12 months. When used parquet, the contribution of TVOC were 11% from the floor covering, 50% from the ceiling and 36% from the walls after 12 months. The contribution of Ammonia were 9% from the floor covering, 60% from the ceiling and 28% from the walls after 12 months. When used parquet, the contribution of Ammonia were 20% from the floor covering, 53% from the ceiling and 24% from the walls after 12 months. The contribution of Formaldehyde were 10% from the floor covering, 72% from the ceiling and 17% from the walls after 12 months. When used parquet, the contribution of Ammonia were 12% from the floor covering, 68% from the ceiling and 20% from the walls after 12 months. The case study also shows the higher air exchange rate impact on pollutant concentration. . Keeping the all the factor same, increase of air exchange rate from 0.5 h-1 to 2.5 h-1reduce the pollutant around 80% of TVOC, ammonia and formaldehyde concentration. If minimum requirement ACH value was taken than the pollutant concentration could be higher than the S3 level. Keeping the standard value for low energy building standard ACH=0.5 h-1 [Thullner, 2010], it could not be possible to reach the minimum level S3. Based on this paper, compare the different type of ventilation system and discovered that minimum amount of pollutant (TVOC) concentration 74 µg/m3 when building with exhaust & supply air system which was too low compare with buildings without exhaust & supply air system (167 µg/m3) and building with exhaust air system ( 183 µg/m3). Non measured TVOC sources was remarkable for the buildings with a mechanical exhaust system its contribution around 45% where as buildings with a mechanical exhaust & supply system, non measured TVOC sources contribution around 25% [Järnström et al, 2007].
Different type of building were tested between 1996 to 2006 and found that the air-tightness n50 value for the timber framed building and heavy weight single family house were much more higher than the single apartment. Higher n50 value increase indoor humidity which increase the chance to more condensation on the building materials surface and this higher condensation are the right place for mold and organism growth. This higher humidity also responsible for the material's emission especially the floor finishing materials and the wall paint. 100 timber wood tested and only 5% fulfilled the low energy criteria for low energy building. This 95% building had 100% possibility of mold growth. Those wood house showed higher airtight which had polyurethane as a insulation compare other vapor barrier or insulation. Some research found the reason of the joint between exterior wall and the ceiling and this point was the most common point to moisture condensation. Autoclaved aerated shows better tightness condition than other heavyweight house. But autoclaved aerated concrete with timber frame ceiling structure shows the poor tight building. Among the total investigate building single apartment showed the minimum n50 value. Actually multi storied building's apartment showed lower n50 value because those building had design and built more carefully.
If the building is not proper airtight such as having basement leakage, foundation drainage, poor joint problem than moisture problem are usually occur inside the building. Moisture could be move in different state like vapour, liquid, ice or snow [Lstiburek et al, 1994]. Haverinen et al, found that the indoor & outdoor air humidity, liquid water used, leaks, rain water, surface water, rising damp were the source of moisture [Haverinen et al, 2001]. A grading system was induce to show the moisture damage in dwelling. Grade 1 characterized as absence of visible moisture damage. Samples with notable moisture content are classified as grade 2 and Grade 3 having a significant moisture problem [Nevalainen et al. 1998]. The mean number of damage sites for grade 1 was 0.28 for both houses and apartment. For grade 2, the mean number of damage site for house and apartment were 1.4 & 1.7 and for the grade 3, it was 2.4 & 2.6 respectively [Chelelgo et al, 2001]. Grade 3 shows the maximum percentage of moisture damage in every locations. The paper found the maximum damage occur in (both type of dwelling) in Bathroom. Bathroom also the key place of having maximum moisture damage for every grade and dwelling. It could be the reason water vapour after shower, water leakage, building materials poor ventilation. The other place such as rooms, bedroom, basement, etc also showing the much more damage sigh in apartment compare with house.VTT building and transport have been studied for long time and found that the ambient RH 80% to 95% could be the reason for mold growth but sometimes it also depend on the other factors like temperature, exposure time, material moisture content. At +5°C with maximum RH 100%, mould index of the material was high but at least 84 days later. But At +20°C with maximum RH 100%, mould index of the material was reach the higher condition within the 28 days. It can be conclude that moisture content, relative humidity, temperature and duration of the exposure are the main factors which are responsible for the mold growth[Hukka et. al, 1999 & Viitanen et. al, 2000].
There are two ways to keep a good indoor air quality. First of all proper material selection and proper ventilation. In this paper, Finnish standard materials are suggested because it is accepted by many different country. Keeping at least one week proper ventilation before occupancy, bring better result. Balanced ventilation, dehumidification, ventilation of crawl space always reduce the pollutant concentration. Proper building tightness, joint and structure design also another way to minimize the intensity of this problem.
9.0 Conclusion
This paper gives some particle instruction to constructional professional to achieve a good indoor air condition for residential building. It help to raise the knowledge about material selection, controlling the different influencing factors, envelop air-tightness which improving the structural function, energy efficiency of the building and achieving a good indoor air quality. Indoor air pollutants can be controlled by source controlled and proper ventilation system. Source controlled can be possible by proper material selection. It is the best way to make a material emission database for all type of building materials where including the impact of different factors too.
Higher emission were measured in floor covering material. Parquet shows better result as a floor material compare with PVC materials. The emission level also higher from the onsite structure rather than the manufactured earlier structure. Normally emission intensity are going down with interval of time. Initially higher emission mainly caused of material's inside energy, air velocity and this air velocity co-related with diffusion and evaporation coefficient. In cold climate country, the concentration of pollutants are higher compare with summer. Humidity and temperature most effective factors which shows higher variation of emission with minimum change of this two factor. The biggest part such as wall surface and floor surface are highly affected by humidity. "Increasing air exchange rate from 1 to 2 h-1 the VOCs concentration decreasing 9-40% and the VOC surface emission rate is increased almost 6-98%"[Chi-Chi Lin et al. 2008]. Though higher air exchange rate increase the emission rate from the materials, the overall indoor air pollutant going decrease. Building material characteristics is very sensitive. The same material show different behavior in different case. When PVC use as a floor material, it emitted some different pollutant compare to PVC use as a ceiling material. Though the Composite building material are combined of different material such as floor covering, adhesive, sealant, the emission pollutant shows the reduce value compare with individual material's emission. Water based paint and unsealed floor covering also emitted higher concentration of pollutants.
Poor air-tightness of building envelope may cause higher indoor moisture. Among all other factors, relative humidity is the most influencing one and poor air-tightness is the main reason of higher moisture indoor air. Such type of problem shows a vital impact on Nordic countries. Proper ventilation, airtight building and proper material selection can solve the problem.
It is duty of all scientist, researcher to find out the ways to keep a good indoor air condition for people and make them understand the health effect. Increase awareness the contractor, home owner, engineer about indoor materials selection, airtight building joint and envelope, balance ventilation could be the solution of such type of problem.
10.0 List of future work
To find out the maximum understanding about indoor air quality, the following works should be carried.
1. Testing of wet product
The materials emitted different in wet condition. The wet material such as paint, adhesive etc should be tested. Coating thickness another important things should be tested.
2. Testing of composite product
Some composite product such as (adhesive+ sealant+ floor material), (paint+ adhesive), (adhesive+ sealant+ ceiling materials) and different combination of building material should be tested.
3.Product database and guide lines
Build up a product database and guide lines for engineer, architect, contractors. Every product behaving based on different factors should be summarized and introducing the quality numbering system.
4. Air-tight building behavior
Airtight buildings behavior in term of indoor moisture condition. Relation between ventilation system in airtight building and moisture content at different seasonal time.
The main feature of sustainability are environment, economic, and social dime
