Garages — Why You Shouldn't Get Attached

Q&A With Byggmeister Sustainability Consultant Rachel White

Oh, the luxury of sliding into a warm, snow-free car as your neighbors go to work with their ice scrapers — who doesn't love an attached garage in the middle of a New England winter? Attached garages add comfort and convenience to our lives, but according to Byggmeister Sustainability Consultant Rachel White, new studies reveal they can also pose very real health risks inside our homes. Here Rachel shares important advice for minimizing those dangers if you have an attached garage and some critical things to consider if you are planning to build or renovate one.

First, what is a sustainability consultant?
I evaluate a project from an environmental- and health-impact perspective during construction and also after it's completed. I make recommendations and develop strategies to reduce any negative impacts.

We love attached garages. How can they be bad for us?
There is an indoor air quality concern when they are attached to the side or underneath the living areas. It has to do with air infiltration between the garage and the home, basically, the possibility that pollutants penetrate the walls including carbon monoxide from tailpipe emissions, benzene and other volatile organic compounds.

Why is this suddenly coming to light?
Over the last 10 years or so, there has been an increased understanding of how air moves — air infiltration, and more importantly, there is a greater understanding of how our exposure to pollutants in our homes and buildings may negatively impact our health.

What are the long-term risks?
People are very familiar with carbon monoxide. That's why we have detectors in our homes, because it's a poison. There are a whole host of other volatile organic compounds present in our homes or released into our homes, not only from tailpipe emissions, but building materials too. Some have been associated with asthma, cancer and other ailments. We want to keep carbon monoxide down for sure, but tailpipes emit all sorts of other nasty stuff we don't want in our kitchens, dens, and bedrooms.

Are tailpipe emissions the only concern?
It depends on what garages are used for. Some are workshops and the use of chemicals in those spaces can present indoor air quality problems, both for the people working with them, but also those in the attached spaces. Anyplace where the homeowner is using chemicals for hobby activities, ventilation absolutely needs to be addressed.

What steps can you take?
Some leaks are visible, so start by sealing off anything you can see with the naked eye, like light coming in around the door between the house and garage, or anywhere pipes or wires go through shared ceilings or walls. You can use weather stripping or spray-foam sealant. When Byggmeister does a project, we set up a blower door to test for air leakage and make sure any measures taken are actually working, as well as finding others that may not have been obvious. Then there are things like, never start your car without the garage door open and the pass-through door shut. And, don't leave your car running in the garage at all.

What about ventilation systems?
A local vent, similar to what you might have in your bathroom works well. You can turn it on when you need ventilation, but if the garage is occupied a lot as a workshop, you can get an exhaust vent that is going continuously. Also, if you have an attached garage you don't want to have your furnace or HVAC equipment in there. Those circulate air and you don't want garage air circulated into the home. It can be a big job to move it, but depending on the scale or scope of a renovation project, we would recommend moving it as part of the project.

Do you have an attached garage?
We do, and we've done as much as we can to seal the penetrations between the garage and the house, but there's only so much you can do. Last year, I started to smell gas in the mudroom above the garage and it turns out we had a leak in our lawnmower. We had it fixed, but we ended up moving it into a shed because what became clear is that we still had some air leaks. Ideally, if you have a shed in the back yard, it's a good idea to store your lawnmower or snow blower out there.

What do you say to someone who has dreams of building an attached garage?
If you have the space, build it away from the house with a covered walkway between to avoid walls or ceilings that are shared with any living spaces. If you don't have the space, then make sure you do a really, really good job air sealing. Just keep in mind that no matter how diligent you are, it's nearly impossible to completely seal off the airflow between the garage and the house.

Especially when you have teenagers...
Right after we conducted this interview, Rachel emailed: Wouldn't you know it, when I walked down to the garage I found that my son had left the door cracked open between the house and the garage! It had been that way for over two hours before I found it!

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