This article was originally published in the November/December 1999 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
Home Energy Magazine Online November/December 1999
Health House Cold Climate Standards Keep Occupants Warm and Dry
by Christina B. Farnsworth
Christina B. Farnsworth is a freelance writer and one of only three life members of the National Association of Real Estate Editors.
Monthly utility costs, maintenance costs, comfort, and healthy indoor air are as important as a price tag when it comes to affordable housing. The American Lung Association's latest Health House development sets new standards for affordable, healthy, and energy-efficient construction at the Meskwaki Indian Settlement in Tama County, Iowa.
With their new housing project, the Meskwaki insisted on better-quality homes that would stand the test of time. They wanted to be sure that future homes would last and would perform well for the residents, who tend to be large extended families living together under one roof.
The new Health House homes do not have moisture problems, thanks mainly to thorough air sealing and to mechanical ventilation. Switching to the Health House standards for their new homes has brought the Meskwaki other benefits, too--including greater energy efficiency and a third-party quality check.ALA's High Standards The ALA has developed three different sets of standards to correspond with three different types of climate (see A Brief History of Health House Projects). The Meskwaki homes are built to the Health House Cold Climate Standards.
The ALA standards are highly customized for each home, and are modified to work for the specific climate zone that the house is located in. Buyers also have some options when it comes to special features. ALA data say that construction to Health House standards typically increases first costs 3%-5%, but that this increase is easily offset by lower maintenance costs and lower utility bills. It also provides the occupants with greater control over the indoor environment.
Scheid Construction typically builds scattered-site semicustom homes. The company offers Health House construction to all of its customers, but it says that not all of its customers opt for the long-term benefits that will result from spending an extra $5,000-$10,000 on a luxury home with a total cost of $170,000- $250,000. According to Scheid Construction designer and estimator Mark Kivett, the Meskwaki homes cost less because they are production homes, built without lots of amenities, and because the prices don't include the land (which the community already owns).
The Meskwaki houses range in size from 1,400 to 2,400 ft2. They have three or four bedrooms and two or two and a half bathrooms. The prices range from around $64,000 to $120,000, averaging about $80,000. The houses are owned by the settlement, while the occupying families pay for utilities, maintenance, and--if they choose--the $1,500 cost of an optional air conditioning system. They can choose from seven different floor plans.Priority: IAQ In general, the most common pollutants threatening healthy indoor air quality are combustion byproducts; biologicals (molds, pet dander, pollen); soil gases (including radon); volatile organic compounds (VOCs); formaldehyde; lead dust; and asbestos. All of these can cause mild to severe health problems. Excess moisture can encourage mold, as well as causing structural rot within walls, in attics, and around window framing. It also brings condensation, unpleasant odors, peeling paint, damp basements, and ice dams on roofs. Poorly designed mechanical systems are another problem, inviting backdrafting of dangerous gases into living spaces. Along with bringing health risks, these problems increase home maintenance costs. And as if all that weren't bad enough, many unhealthy homes also have high utility costs. Health Houses are carefully constructed to minimize all of these potential problems.
All Health House building criteria, whatever the climate-specific construction recommendations, govern house tightness, air handler and ductwork tightness, zonal pressure balance, whole-house air filtration and mechanical ventilation, sealed-combustion HVAC appliances, and humidity control. Each Health House home undergoes a series of performance tests to determine if it has been built to meet or exceed these standards.
What distinguishes the ALA's Health House Standards for Cold Climates is not the level of insulation specified, but rather the great attention to detail in providing filtration, ventilation, and moisture control through waterproofing foundations, carefully sealing all potential exterior openings, and employing energy recovery ventilators (ERVs). The ALA Health House project views homes as systems and pays as much attention to the home's design and layout as it does to the selection of building materials, construction techniques, furnishings, and finishes.
After ALA chapters built many Health House demonstration homes in different regions, the ALA began the Health House Advantage (HHA) program to bring builders into the picture. Though the HHA program has trained literally hundreds of builders, it is each house, not the builder, that is certified. Construction starts with an energy analysis of the plan. Patrick O'Malley of Sheltersource in Lakeville, Minnesota, is the regional consultant for plan review of potential Health House homes. (Sheltersource is a subsidiary of Sheltersupply, a distributor of building supplies). O'Malley uses either REM Design or HOT2000 to analyze the plans that builders submit for HHA consideration. He often runs both of these programs on a plan to cross-check the accuracy of the results. Along with careful design, the homes are inspected while construction is under way. Inspections are done at three different stages: foundation, framing (but before insulation), and after insulation and sealing (but before drywall).A Healthy Foundation A properly built and waterproofed foundation is key to a Health House. The Meskwaki chose insulated concrete forms (ICFs) with an R-value of 20 for their foundations. The houses performed perfectly, says O'Malley.
Because the houses were monitored so closely, however, some concerns came up early on. According to the builder, in one house built during a period of heavy rain and high relative humidity (RH), there was some dampness observed at the base of the foundation around the perimeter of the basement. Iowa has experienced unusual weather extremes this year, Scheid says. The RH was very high at the time this was observed, and no HVAC system or ventilation system had yet been installed in the home. Scheid adds that he experienced a similar problem when his own home was built, but in both cases the moisture went away after the HVAC and ventilation systems were installed.
Furthermore, Scheid points out, it has long been known that concrete dries more slowly inside forms. Many architects specify that forms be left in place for a period of time after the pour to take advantage of concrete strength increases resulting from the slow drying process. Since the foam forms on ICF walls remain permanently in place, the slow drying of the concrete ultimately creates a strong, dry wall.
The Health House standards call for gravel fill beneath the foundation slab. The fill is covered with a polyethylene membrane before the foundation slab is poured, to prevent water vapor from migrating into the home. The standards also call for drain tile to be installed outside the foundation to carry any water away from the house. Specified mastic coating on the foundation walls repels moisture.
The Health House standards allow for a number of framing techniques for insulating to roughly the same R-values as those dictated by other climate-specific model energy codes. For the Meskwaki project, which is built in a climate that averages 6,560 heating degree-days (HDDs), the wall system is 2 x 6 on 16-inch centers wood frame construction insulated with R-19 fiberglass batts. The exterior siding is vinyl, which was selected for its low cost, easy maintenance, and resource efficiency.
Properly installed insulation and air sealing helps to eliminate interior condensation problems within walls by keeping air from meeting surfaces with dramatically different temperatures and trapping condensation inside the wall cavities. The Health House standards call for a house wrap (Tyvek has been used at the settlement) that is properly flashed to form a drainage plane to prevent wind-driven rain from penetrating the wall. On the interior face of exterior walls, the standards call for an air barrier and a vapor retarder. Polyethylene was used as both in the Meskwaki homes. Mere wrapping is not enough to provide air barrier continuity, however; the seams must be carefully sealed with tape, and any penetrations must be carefully sealed, as well.
One way to seal penetrations is by using the LESSCO air/vapor barrier box, a Tupperware-like device that is fitted around every single receptacle and switch in every exterior wall. The box takes just a few seconds of extra time to install and adds $2.00-$2.50 per box in product and installation costs, O'Malley says. They make it easier to install and seal the continuous air/vapor barrier, O'Malley says.
High-efficiency windows with low-emissivity (low-e) coatings are also part of the Health House program. The windows installed in the Meskwaki homes are Wenco vinyl framed, double glazed, and argon filled, with a low-e coating. The homes feature either single-hung windows averaging $140 each or casement windows ranging in price from $170 to $200 each, depending on size. Careful sealing--including using foam in window and door rough openings--reduces air infiltration of the windows and doors by an additional 30%.
The Health House standards also encourage use of certain types of finishes and materials. The Meskwaki chose to use low-VOC paints. Lighting is also covered in the standards. Even when covered with insulation, standard recessed lighting fixtures still allow significant amounts of conditioned air to escape and allow unconditioned air to enter through the fixture's perforations and through the space between the fixture and the ceiling opening, O'Malley says. ALA's Health House project recommends using recessed lighting fixtures that have no perforations and include a foil gasket to seal between the recessed housing and the ceiling. It also recommends selecting low-wattage bulbs to lower utility bills, and choosing fluorescent bulbs.
A truss system with R-50 blown fiberglass insulation and sealed windwash barrier at all exterior edges completes the building envelope of the Meskwaki homes. The homes employ windwash barriers because, under certain conditions, wind can wash through the attic and diminish effective insulation R-values above the top plate. To keep the top plate warm and the attic cold, the oriented strand board (OSB) sheathing extends to the bottom of the rafters of the top cord of the truss. Sealing between the rafters is carefully done to leave a 1-inch air space for ventilation.
Tightly sealed ductwork is a crucial part of every Health House home. In Health House homes, mesh and mastic are used to seal all duct seams. Sealing also helps to prevent duct leakage induced by negative or positive pressure. The program also requires that all cold-air returns (returns from the living space to the air handler) be fully ducted to prevent contamination. As a final step, ducts must be cleaned and vacuumed to remove any particles that may have entered during construction.
A blower door test is done during the fourth and final inspection to check airtightness; the finished house must leak no more than 0.24 CFM/ft2 at 50 Pascals (the normalized leakage value is typically .10 ACH in winter and .05 ACH in summer). Other tests done at this time are for duct leakage, series leakage, worst-case depressurization, ventilation flow, and zonal pressure. With this array of tests to look forward to, Health House Advantage builders go into the program knowing they will have to meet very high expectations.
Another step that brings a Health House home to a higher standard is the use of efficient equipment. The Meskwaki chose a 92% efficient traditional forced-air, sealed-combustion gas system to meet its goal of housing affordability. The systems run mostly on liquified petroleum (LP) gas.
All these features and techniques work together to ensure healthy air, eliminate moisture problems, and substantially reduce energy costs. The expected total annual energy costs for a 2,248 ft2 Meskwaki Health House home are $1,050 annually, or an average of $88 a month. To date, only 26 or 27 homes are complete, and none has been lived in for an entire season, so it is impossible to verify as yet that these expected costs will pan out. However, it is interesting to note that the local LP provider thought the new homes had different systems because he wasn't visiting the settlement to refill the LP tanks as often.Fresh Air to Breathe All Health House homes must use only sealed-combustion appliances--and that includes fireplaces. The ALA's Health House standards call for direct-vent, sealed-combustion gas fireplaces to keep harmful combustion gases from entering the house. Because most homes do have attached garages, Health House standards recommends that CO detectors be installed in all homes, as are fire detectors. The healthiest alternative, the ALA says, is to use a detached garage. The Meskwaki garages are optional (at extra expense) and are detached from the homes.
ERVs act as the home's lungs by providing a continuous supply of filtered outside air while exhausting stale, contaminated indoor air. During the winter in cold climates, such ventilators capture up to 80% of the heat energy from the exhausted air, and transfer that energy to incoming air.
Though ERVs are the standard recommendation for Health House homes, the Meskwaki, working with O'Malley and the ALA, chose to install heat recovery ventilation (HRV) systems instead, to keep costs lower and to suit the occupant's lifestyle choices. The Health House performance standards require the ventilation equipment to provide a complete change of air in the home once every four hours on low-speed operation, and every two hours on high-speed operation. The ventilation system is tested using a flow grid. Occasions requiring high-speed operation might include large families taking lots of showers, holiday cooking and baking, canning sessions, or other activities that would increase moisture levels in the home.
A house also needs source point ventilation in kitchens, bathrooms, and laundry rooms to exhaust water vapor, odors, and other concentrated contaminants. Kitchen exhaust fans are important to rid the home of the odors, water vapor, and particulates (such as grease and smoke) that normal cooking produces. However, bigger is not always better (see Oversized Kitchen Fans--An Exhausting Problem, HE Jan/Feb '99, p. 37). The Health House standards require careful sizing and installation of range hoods so that they have their own makeup air for safe operation. All the Meskwaki homes have a two-speed manually controlled vent fan over the range, and the ventilation system is ducted to the kitchen, bathrooms, and laundry to exhaust these source points. There is also a dehumidistat control on the ventilation system to automatically balance the house's humidity.
According to Meskwaki housing director Larry Lasley, the fans are easy to use and don't make a lot of noise. We recognize that it is important for us to educate the homeowners to remember to take that extra step and set the ventilators at high, Lasley says. The high-speed fans have timer switches so that they can be set to run up to an hour. The homeowners also are instructed on how to maintain the fans by changing the filters and monitoring the intake vents (to see if they need cleaning) on a monthly basis. Instructions for these steps are also given on the equipment itself. The Meskwaki chose a filtration system using 3M Filtrete.
For homeowners suffering from allergies, asthma, or other respiratory problems, the Health House standards recommend extra filtration. Filters for this purpose should be 99.97% efficient at removing particles 0.03 microns in size. The ALA also recommends that an antimicrobial polyester prefilter with a 5-lb, activated-carbon filter be attached to the filtration system.
Central-vacuum systems with advanced filtration are recommended to minimize dust and other allergens. Typical vacuuming can stir up dust particles and redistribute them into the air at nose level. However, the receptacles for central vacuums can be located outside the living space. Vacuums with advanced filtration will minimize the redistribution of particles back into the home. For first-cost savings, central vacuums were not installed in the homes at the Meskwaki settlement.
Even lifestyle and cleaning practices are addressed in the Health House standards. The best Health House home can fail to provide clean air if its occpants bring in harmful furnishings or finishes, or if they engage in unhealthy practices such as using polluting chemicals indoors. (see Occupants Pollute Healthy Homes, HE Sept/Oct '98, p. 6). Therefore, the ALA recommends that people who choose to live in Health House homes make an effort to learn about potential pollutant sources.Future Developments The Meskwaki community was the first to use The ALA's Health House standards to build affordable houses. In the process, some cost-saving decisions were made--such as not to use central vacuums, to make air conditioning a $1,500 option, and to install HRVs instead of ERVs. So far, the homes seem to be performing well.
Thus far, some 27 homes have been completed and another 50 are in progress, scheduled for completion in the spring. The Health House program continues to be an ongoing evaluation process that refines and balances the sometimes competing choices for health and affordability. The last word on the Meskwaki homes is that residents breathe easy while finding their new homes affordable to buy, to operate, and to maintain.
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