Ahhh, it’s toasty in here!
This blog entry is long overdue. A few months ago we turned a corner on the house construction when the wall cavities were insulated. While this is not particularly exciting work to most folks, we confess we were a little giddy.
Here’s the skinny on house insulation products. You have three main types of insulation products: fiberglass batt, cellulose, and spray foam. When assessing these products, we compare them by how insulative they are, or how much they resist heat transfer. We call this R-Value, which relates to thermal resistance. The higher the R-Value the more insulative the material is (the more resistive to heat transfer). So, big number = good when you live in New England.
The external walls were constructed with 2x4’s, leaving just less than a 4” cavity to add insulation. The new Energy Stretch Code (and LEED Certification) requires R-21 in wall cavities for new construction or filling the cavity with your chosen product for renovations. The ceilings require an insulation value of R-30, or again, filling the cavities in renovations. So we had to fill the existing cavity. The question was, with what?
The products come in at:
- Fiberglass Batts: R-4/inch
- Cellulose: R-3.5/inch
- Polyisocyanurate Closed Cell Foam: R-6.7/inch
Clearly the closed cell foam wins, with a price tag to prove it! Most contractors opt for cellulose if the drywall is not being removed - it’s really the only option to completely fill a cavity without removing walls. If walls are being removed, fiberglass batt is standard for cavities that are not confined, like an attic ceiling. We could have used fiberglass batt in the walls, but that would have left us with a total wall insulation value of R-15 and a sealing nightmare (while insulation is about resisting heat transfer THROUGH a material, sealing is about preventing air flow out of the home through holes and gaps).
Right, sealing. So you want a tight thermal envelope (fully closing the perimeter surface of the house). Tracking down holes in an old house is kind of like asking your toddler to quietly sit in a chair while you leave the room. Both fiberglass batt and cellulose require extensive sealing measures to tighten the hatches so to speak, and even then, the home will never be as tight as you can get it with closed cell foam. So a huge advantage of the closed cell foam is that it’s just that…it is closed. No additional sealing measures are required. While the product is much more expensive, it is SUCH a better performing product that it is well worth the money, particularly for renovations (since all those old holes are so difficult to track down)….and it makes us feel good that the homeowner will be getting the best available insulation product currently on the market.
On the other hand, what's the rub? (every product has its drawbacks, after all) Well, let’s just say you could be a happy person if you took one too many hits off the spray foam truck! The life cycle environmental costs of spray foam products given their tremendous energy savings is still a heavily debated topic in the world of green construction. When Henry, our builder, told us that he fires up his heater inside the house for a short while in the morning to keep the crew warm, and then turns it off for the rest of the day and it is still warm, we knew we made the right choice. We are soooo happy with the closed cell spray foam and the job that Capital Insulation did! In the end, while close cell spray foam is not a renewable product (it is derived from fossil fuels), we think it is a better use of non-renewable resources - giving a hundred years or more of high energy performance to rehab a house that is already a hundred years old - than many of the other applications we currently use our non-renewable fossil fuels for...
So, here are the final insulation specs:
- R-26 in the vaulted ceilings in the master bedroom, kitchen and dining room
- R-20 in all of the walls
- R-30 in the ceiling of the family room, downstairs bedroom and bathroom
- R-21 in the basement ceiling
That’s pretty good for a renovation, if we do say so ourselves!
Now for some pictures. Here, you can see how well the foam sits around irregular surfaces like a pipe or an outlet.
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| Pipe surrounded by spray foam insulation |
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| Electrical outlets surrounded by spray foam insulation |
After being sprayed, the foam required shaving in some places to bring the surface back behind the studs. Here, you can see the foam surface along the wall.
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| Spray foam insulation along a wall surface in the master bedroom |
Foam had to be installed around the collar ties in the vaulted ceilings, again another reason why the spray foam is so much easier to work with:
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| Vaulted ceilings in kitchen / dining room, with spray foam insulation installed |
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| Vaulted ceilings in master bedroom with spray foam insulation installed |
Another difficult spot to insulate is the sill band, where the framing meets the foundation. Capital Insulation did a great job at this difficult and critical junction.
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| Spray foam insulation at the sill band |
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| Spray foam insulation around structural work in basement |
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