Decumanus Green | Insulate, Baby, Insulate.
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Insulate, Baby, Insulate.

The exterior of the shell of the Greenberg residence is just about finished. We have made it as airtight as we could get it. We won’t know how successful we were until we run a blower door test in a month or so. We now move inside and begin the process of insulating the shell. Over-the-top insulation and air sealing are the keys to the performance characteristics of this house.

The client, Laurel, has made the financial commitment to do what it takes to have a Mass Save New Homes Program Tier III house. This program provides generous incentives for building houses that meet specific energy performance standards. The Tier III standard is going to be challenging to meet. The house has been designed to meet it. The only variable we don’t yet have complete control over is the tightness of the shell. Thus the importance of the blower door test that lies ahead. Eventually we will have to have a certified blower door test showing the tightness of the house to be just under 2 ACH@50 (when the house is pressurized to 50 pascals, it will take roughly ½ hour to displace all the inside air with new air). This testing will be certified by an independent HERS rater (His&Hers Energy Efficiency, info@HHefficiency.com)

The insulation we are installing will go a long way to helping us achieve Tier III. One of the ways we have attained cost savings on our way to future energy savings, is to purchase used insulation for under the concrete slab first story floor. Paul Huijing buys and sells this insulation product. From Paul we got both the insulation that will cover the concrete walls (2.75” polyisocyanurate) and the 3” EXP that will run under the slab. This is kind of nasty looking stuff (see picture). The insulation is covered with a thick coat of stucco. The stucco is great at collecting and holding dirt. It also makes the 2×4 panels of insulation quite heavy. Although we saved a significant amount of money purchasing this product, some of that savings will be eaten up by the labor costs associated with handling the product.

Under the stress and fatigue of unloading the material with Paul and some Decumanus crew members, again, it is heavy and dirty, I debated with myself the wisdom of going with the used. But it is worth it. The small differences, the small savings do accumulate. So it does make economic sense. But not only. It is also a smart thing to do. It creates a marketplace for the material, which encourages further recycling. The insulation is a petroleum base product. Increasingly it is important that we reuse petroleum products when we can. We are also making a down payment on infrastructural changes, both within our company and outside of it. We will get better at handling this material and so will Paul. The costs to me as a builder will fall and make even a stronger economic argument. A choice today that saved us a small amount of money will set the conditions for saving even more money in the future. And the whole thing is just better for the environment. This is a measure that truly meets meaningful multiple bottom line criteria.