April 17, 2012

Is your house suffocating itself
and you?

In most cases, it is. Like human beings houses need to breath. Without a certain amount of air exchanges a day, you and your home can get sick. It is only recently that we have begun to focus on how our living environments, both indoors and out, affect our health. A big factor in home health is proper ventilation.

In milder climates homes are built loose and with limited concern for energy savings. This allows them the benefit of having natural ventilation. In areas like Tahoe energy conservation efforts are necessary and local building codes require that we now insulate homes with large amounts of insulation and air continuous barriers to prevent heat loss. This limits the amount of fresh air a home will exchange with the outside environment.

Ventilation comes in many different forms and has different uses

It is very common in Tahoe to ventilate our attics and crawlspaces. These ventilated areas are considered unconditioned space or space that is not temperature-controlled. If vents are not available nor opened in summer months condensation will form on cold surfaces resulting in mold growth. Most homes should have vents run around the perimeter of the crawlspace and allow opening in summer months and closing in winter to prevent pipe freezing. If your home has an attic you will need vents in the freeze blocks by the eaves, vents at the gable ends, or a vent in the ridge of the roof. In most cases you will need a combination of these.

Attics and crawlspaces are typically unconditioned spaces. They should be separated from the living space or “conditioned spaces”. This is done with an air and a thermal barrier. The air barrier would simply be the floor you walk on, or your drywall ceiling. Not much air passes between these materials so it is an air barrier. The thermal barrier is the insulation that should be in your floor and ceiling joists. It resists the exchange of heat and is therefore called a thermal barrier. Together they are the home’s living space envelope.

If your home is working well, this barrier will be continuous with both layers intact and next to each other surrounding the entire living space. This barrier will separate the cold outdoors and hot attic from the area of the home you live in. The more holes in this barrier, the more energy loss your home will have.

The best way to ventilate your home is passive ventilation. Simply by opening windows in the summer time for at least a couple hours a day, you will give your home the fresh air it needs. The issue is that there are only a few months when keeping windows opened is feasible. So what to do the rest of the time?

In many cases if you have an old home with limited mechanical ventilation systems you will need to open windows from time to time in winter months. This will result in heat loss but will be much better for the air quality in your home. More modern homes will have exhaust fans. These include the fans in your bathroom or the hood vent over your stove. When you turn these on it forces air outside of your home.

To replace that air, other air needs to come in somewhere. Many times the entry points are accidental holes in your home’s envelope. Some common breaks are electrical outlets, recessed lights, and leaky heating ducts. When these items are installed, holes need to be cut in the drywall or air barrier resulting in air transfer between conditioned and unconditioned space.

So in most cases we are trying to get fresh air from the least-fresh places like your attic and crawlspace. To solve this problem there is a device called a heat recovery vent. This is simply a vent with an exhaust and an intake. The fresh air comes directly from outside and is heated as it enters the home. The air that is exhausted from the home has some of the heat taken out of it to be used to heat the air coming in. These systems are being improved every year and as the technology gets better and information about air quality gets to be more commonplace, these units may one day be in every home.

Another reason we ventilate spaces is because of combustion appliances. These include your furnace and water heater if they run on combustible fuels like oil or gas. For them to operate many times they require a source of air to allow for the combustion process. If there is not enough air available in the room that these combustion appliances are operating in, they will deplete the room of oxygen and produce harmful. This poses an issue for breathing and also combustion. If there is not enough air available for the combustion process then the fuel won’t burn properly producing harmful carbon monoxide.

Some appliances have intakes for their combustion air, though for most water heaters and older furnaces, there needs to be a vent to the outside in the combustion area. This is achieved with simple louvered vents that connect with the unconditioned space of the crawlspace, attic, or outside. If connected to the attic or crawlspace, you need to confirm that that those areas have proper ventilation to allow for the combustion appliance.

The other issue with a lack of ‘make up’ air is negative pressure and back drafting. Many combustion appliances rely on natural drafting to vent combustion exhaust. For this to work the exhaust pipe needs to be engineered properly allowing enough vertical rise to create a draft. If the exhaust is not designed well it won’t have enough draft to allow the appliance to be exhausted to the exterior.

In addition to improper exhaust installation, when a room doesn’t have enough make up air it will create pressure. With fans and other appliances which exhaust air, a large amount of negative pressure is created in the appliance area and can actually force the combustion gasses into the room instead of up the exhaust pipe. This leads to a build-up of carbon dioxide that is also harmful in elevated levels.

So now that you know that ventilation is important, you need to determine whether you, your customer's and your client's homes are suffocating. If you are interested, we offer a detailed home audit service for $150 – $250. Please call today to schedule an appointment at 530-581-1094.

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Tahoe Mold and Water
P.O. Box 5187, Tahoe City, CA 96145
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