In the master bedroom we decided to vault the ceiling. Part of that decision involved contracting a company to install spray foam insulation. When it comes to insulation, there generally three* categories of interior insulation: foam, blown in, or rolled fiberglass. Rolled fiberglass is the most commonly encountered insulation. It’s the big rolls of pick fluff generally sporting the pink panther on it. These are sold in any home improvement store and are incredibly easy to install yourself. Blown in insulation comes in a variety of different materials usually divided into organic or non-organic substances. You can rent machinery to blown in your own insulation, or higher a company to do it. In either case, it involves literally blowing stuffing into your walls and attic spaces. For the walls, this usually involves cutting holes in the exterior of your house, hooking up a machine similar to those stuffing machines at the build-a-bear stores in the mall, and filling your spaces with a densely packed material that will then expand a little bit and fluff up. Essentially you’re turning your house shell into a big pillow. The final type of insulation is foam. Foam typically comes as a two part formula. When the two chemicals mix together, they create an exothermic reaction that forms a high volume foam that quickly hardens as it cools. For small jobs, like filling cracks or insulating around doors and windows, you can buy cans of foam from a company called Great Stuff (again, available in any hardware store). For big jobs, like your attic or walls, you’ll usually higher a company. There are DIY kits available now, but they’re relatively new and I’m not sure if they’re legal to access in every state. In any case, the big version works just like the small version. A two part chemical is mixed and sprayed. It foams up and hardens. The difference is that the big version uses a lot more chemical and you need specialized equipment to propel and mix the foam.
Each of these different kinds of insulation has trade-offs and I won’t go into a detailed evaluation of each. A contemporary theory in residential design is focusing on controlling air movement in and through a space. You might have heard of “air sealing” or “air tight” homes. The essential idea is that if air is coming into or exiting the home through the walls or seams, then your heating and cooling efficiencies are being negatively effected. Imagine how hard your fridge would have to work if you just left the door permanently opened. Fridges have magnets and gaskets in order to seal in the cold air. In the same way, builders today design houses to seal in as much air as possible. The way in which you insulate your home then matters a great deal to how air moves through it. This swings us back to foam. Foam is the preferred material for air sealing a home. It isn’t impermeable, but depending on the mixture, it can come pretty close. When you start researching foam, you’ll quickly encounter two general types: open cell and closed cell. The history is actually pretty interesting. Foam insulation was originally used in industrial applications and there was only one type. It was very dense and nearly water proof. As people started to expand it into residential and commercial applications, chemists started tinkering with the formula in order to introduce bigger pockets of space within the foam. If you can manage to create larger pockets, then the same volume of chemical will cover more area and therefore it’ll be cheaper to use. Industry doesn’t care about $20,000 of insulation, but the average home owner does. “Open-cell” then, is a family of foams that have much larger and non-uniform air pockets. It’s much cheaper than the original “closed foam”. These terms are kind of a misnomer though. It’s better to think about the chemical composition on a sliding scale. A company that specializes in foam applications will either offer several options on this scale or have a custom blend they prefer. The trade off is that the open cell end of the spectrum is much cheaper, but also doesn’t insulate as well. For example, water can pass through those foams that are sold as Open Cell. This is a really important consideration for trying to achieve an air tight home.
When it comes to our project in the master bedroom, we wanted to reclaim as much of the attic space into head room as possible. In that part of the house it wouldn’t be possible to finish the attic into a usable room. There just isn’t space. The important decision is how to protect the roof. One of the old building ideas is that houses have to “breath”. They were designed to purposefully allow air to circulate between the interior of the house and the exterior. This is why roofs are vented. When it comes to roofs, this idea is very important because it allows moisture to escape. The exterior of your roof is covered in a water proof layer of tar or some other sealer. No water is going in from the top unless you have a hole. But the interior of your roof is just raw wood. If you trap moisture against that raw wood, it’ll cause rot. Once the wood rots out, the roof has to be completely torn off and rebuilt. Not to mention in the mean time you create the perfect environment for mold growth. This kind of thing happens a lot with bathrooms that have fans that just vent up into the attic instead of outside or poor circulation in your attic space. So, having air freely moving prevents water from rotting out your roof from the inside. However, in the age of air sealing a home, the same problem is addressed differently. By creating a water tight seal on the underside of your roof sheathing, you stop an possibility of roof rot. Here is where foam really shines. You can fill the space directly under the roof sheathing with an impenetrable foam and never have to worry about venting. Then you can finish right on top of the foam. The alternative method would involve creating channels of air across your roof by installing what are essentially plastic gullies that connect to vents in the overhang of your roof. Then you can install traditional insulation on top of these and finish on top of that. It works fine if done properly, but the entire package is going to take up much more space than foam. To give you an idea, from shingle to drywall, our roof area over the master bedroom will be about 10″ thick. The traditional method would have been closer to 18″ thick. If you buy into this air sealing concept (which I do as there is building data and research to support it), the added energy efficiency of foam over traditional insulation is going to reflect in your heating and cooling bills as well.
In case anyone in the Cleveland area is interested, we used a company called Pure Seal. They’re a family operation the the guy who runs it is incredibly knowledgeable. They use a proprietary blend that the owner explains as “semi-closed cell”. They did our master bedroom and all of the rim joists in the basement. Our house has a thick layer of blown in cellulose insulation in the attic and walls, so unless we’re gutting an area, it doesn’t make sense to tool with our insulation too much. But if it comes up again, we’ll certainly use this same company. In any case, while it’s not the most sexy of home improvements, proper insulation, especially in very cold or very hot climates, is one of the best investments you can make in a property.
* There are a few other types of insulation out there including polystyrene sheeting, geo construction (using earth and mud), reclaimed materials, and whatnot but the three I mentioned are what you’ll commonly encounter. The world of insulation is actually pretty fascinating and everyone seems to have a host of logic, numbers, and propaganda about why their way is the best way.