How can we prevent car fumes from polluting our house through the attached garage?
We are in the process of building a new house. It never crossed our minds—until now—that it is a bad idea to have an attached garage with bedrooms above. What can we do to stop car fumes from polluting the air in our house? We are still framing.
A teacher once said to me, "Although I do not use the word never too often, I would never build a house with an attached garage for my family." I fully agree with him.
- For future reference, it is always preferable to build a freestanding garage away from the house. This eliminates the risk of polluting your home with carbon monoxide and other noxious fumes.
- Building a freestanding garage also reduces your energy consumption: air can leak into or out of the house through an attached garage, leading to undesirable heat gain (or loss).
Luckily, you are still in the framing process, so there are a few ways you can minimize the harm.
Minimizing the harm
I understand that not everyone has enough space to build a freestanding garage.
- Where you're in the process of building your home, you might still be able to convert the attached garage to living space and park the car somewhere else.
- If that's not possible, consider placing the entrances to upstairs bedrooms outdoors, above the garage, with an exterior staircase leading up to them. This enables you to seal off the entire space between the garage and the bedrooms above, minimizing potential airflow paths between the garage and the living space.
- If you do build your home with an attached garage, never let your car idle or warm up in the garage.
- And most importantly, make sure to have your home completely, and I mean completely, air-sealed by a professional.
Air-sealing your garage
Air-sealing is when a technician or crew uses a variety of methods to seal off leaks in the building's shell.
In warm, humid climates like Houston's, it is best to seal the building's exterior surface instead of interior.
- There cannot be any airflow paths connecting the garage to the house.
- Blower door tests should be performed before, during, and after air-sealing to verify progress and effectiveness.
Work with an experience professional
It is important that you have a certified professional do this type of work. I do not recommend that homeowners perform these types of improvements on their own; without the right knowledge and training you can create potentially dangerous situations (such as improper venting of combustion appliances).
- I recommend you have a Building Performance Institute (BPI) certified or accredited contractor do the work on your house. Being BPI-certified myself, I know that these professionals have to go through a rigorous program of tests and trainings and will likely be using the most effective air-sealing techniques.
- Also, if your energy auditor or contractor is part of the Home Performance with Energy Star program, you may be eligible for tax credits, rebates, or other forms of financial assistance.
Ask your contractor to use a water-based, low-VOC caulk for the air-sealing work. Standard, cheap caulk uses other solvents and can contain toluene, hexane, and formaldehyde, all volatile organic compounds. AFM Safecoat Caulking Compound is an environmentally friendly caulk that outperforms most traditional products.
Insulate the walls connecting your home and garage, too
Once you have made sure that the air-sealing has been done correctly and effectively, insulate the connecting walls and ceiling with water-blown, soy-based spray foam insulation.
Spray foam insulation will create an additional air barrier, seal any imperfections in the caulk air-sealing, and provide excellent and long-lasting insulation.
- We use BioBased 1701 spray foam insulation for our projects, but there is another soy-based product called Emega that we also highly recommend.
- If soy-based foam is too expensive or is not available in your area, try Icynene LD-R-50, which is not soy-based, but is water-blown and is one of the healthier insulation materials out there.
For more information:
Read Ray Pruban's Q&A "How do I install an exhaust fan in the garage to activate with the garage door?"
To find out how you can qualify for rebates and incentives for improving your home's energy efficiency, visit the website of your local utility or state energy agency. Another good place to start is the Database of State Incentives for Renewables and Efficiency (DSIRE).