It's a very big decision to choose to build a home, and an even bigger one to do that in a upstart intentional community. None the less, several families have recently made the leap and we're enjoying the pleasure of building some of these beautifuly simple, energy efficient, custom homes for them.
The approximately 1,000 sq. ft. house we are currently working on is for the Italiano-Boerst family. As you can see from the photos it is fully framed with windows and roofing in place- We completed the rough electric work this week in temperatures that felt as if we were at the south pole. Next week we will be insulating both the walls and ceiling with blown cellulous. Typically we Creative Constructions only need blow cellulous into the ceiling area -because we generally construct walls with SIPs or (structually Insulated pannels). We love the R-value performance and ease of construction of SIPS. However, in the case of this buildng the family just didn't like the idea of using a material whose main ingredient is eps foam-- 5 and 1/2" of cozy foam to be exact. Derived from petroleum, the eps foam in SIPs does turn some folks off as being not a green enough choice. That's cool, but to be fair, "greeness" should be measured in more than one dimention and if the reason you dismiss SIPs is becasue it is in-part made from oil, there is more to consider. Infact the long view looks much greener! SIPS are recommened by most green building resources as a good choice for walls and ceilings because when one looks at the energy saving performance acheived year after year with SIPs compared to more traditional 2x6 stick framing ..SIPs shine-- Simply stated, the superior insulation performance SIPs provides cuts energy use, i.e. the amount of natural gas needed for heating- and that is green. Additionaly, the osb panels used in SIPS are made from small diameter, fast growing, often farm grown trees- like aspen, this reduces the need for dimentional lumber in a new home, lumber that must be cut from larger, slower growing trees. Finally the labor savings acheived with SIPs means less work/labor needed to build the house --which we consider a green merit in and of itself
On the other hand...The home we are building this month utilizes a smart unique stick framing/blown insulation strategy that maximize the R-value performance of the walls very nicely with out any petroleum based products --just more labor and more wood. Here is how we are doing it. The walls are first framed using 2x6s, 16" on center, then they are strapped horizontally 2' on center on the outside using approx. 2-1/2" lumber (2x6s ripped legnthwise).
To this grid, we then attatch our OSB sheathing, add house wrap, do careful air sealing of all joints, seams, and perimeters using expanding foam GreatStuff from a hand held gun and finally install the siding, which in this case is locally milled board and bat hemlock.
The horizontal strapping step addresses the issue of "thermal bridging", an issue from which SIPS are mostly exempt. Thermal bridging, is a term that desrcibes the action of heat or cold transfering/moving through a solid object and is a significant cause of heat loss in the winter in residential construction. By adding the narrow horizontal strapping on the outside of the framing, thermal bridging is reduced to only the small locations where each horizonal strap crosses each 1 & 1/2 " wide vertical stud. The added benefit of this framing technique is a thicker than typical wall (7" in this case) that can hold more insulation producing an R-value around 26. It's all more laborious than building walls with SIP panels which provide structure, insulation, and sheathing all in one, but is a good choice if for what ever reason you nix the SIPs.
No comments:
Post a Comment