Building Options

SueVa2013

12 years ago

Hello, We have finally (!!) secured our loans and moving forward with our house constructions in area that could be considered Northern Virginia. We are in Zone 4 and want to build our house that is energy efficient and not break our bank. We believe in the 80-20 rule. Ours is a 3000 above grade house with unfinished basement (we will finish later when the funds are more available). Exterior is Hardiplank (mostly) and Stone. Some of the things we have decided after talking to our builder are:

1) Use OSB with reflective under layer in the roof
2) Use 2 inch foam under the foundation slab
3) Use 2 zone radiant heating to cover approx. 600 sq ft where we think we will be spending a lot of family time.

What are your thoughts and suggestions about the above?

Now the biggest decision facing us are about the external walls. Options given to use by our builder keeping in mind our budget are:
1) Use a Rmax Thermasheath-SI/Dow SIS on 2x4 construction with bat insulation. Giving us close to R18 - This is recommended by our builder.
2) Use a half inch Foam Sheating on OSB Sheating, 2x4 construction , bat insulation. Giving us R18
3) 2x6 construction,OSB Sheating with just R21 bat insulation
4) Our builder is saying spray foam is going to be too expensive and steering us away from this.

Any input is appreciated.

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Comments (3)

virgilcarter
12 years ago
If it was my house, for exterior walls I would use 2X6 stud construction with Tyvek (or equal) and a minimum of 1/2" rigid insulation over either 3/8" ply or 1/2" OSB sheathing, with cellulose insulation in the stud space. Interior gyp board should be sealed.

Exterior rigid insulation is important to prevent thermal transfer.

The roof radiant barrier and foundation insulation are essentials, IMO.

I'm not a fan of mixed HVAC systems ("a 2 zone radiant heating...), assuming you are using another system for year-round heating and cooling.

If you are concerned about energy efficiency there so much more to consider--house orientation, passive systems, active systems, etc.

Good luck on your project.
If your want a "tight" house, it will also be very important to have proper sealing on all exterior joints and connections.

I agree that spray insulation is a more expensive alternative.

Good luck with your project.
dgruzew
12 years ago
We are building now in the Chicago area and did your option 3 . The 2x4 + Thermasheath was more expensive and more difficult to do . you can get R21 + with that though and if you do its better because it covers the studs more.

2x6 + bat was the cheapest even with the extra lumber.

When watching all the shows and reading all the stuff about making your house HE - they never really explain that it cost SO MUCH MORE - that the payback on many items is many many years ( Solar, GeoTherm , Spray foam ) . It just does not make sense .
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ibewye
12 years ago
Not being a smart ass but isn't Virginia fairly warm all year? I'm in the northeast and went with 2x6 walls,tyvek house wrap, 1/2" sheathing and Roxul r-23 for wall insulation. I used ridgid foam under basement slab because I used radiant heat in the slab, I also used foam betwden the edge of the slab and the walls for no other reason other than I read that 80% of your slab heat would be lost into the walls.
Questions for you. What would the purpose be of the 1/2" foam? Is it to insulate for heat or just to reduce wind? If I remember I didn't think foam that thin has much of an r-value to it? Last thing to consider, Certain-Teed makes a concrete siding similar to Hardi-board (the pros and cons of each brand is a neverending debate) which comes with insulation on the backside. Maybe something you should look into. If you really wanna save money keep the shape and roof of your house somewhat simple, the cost of construction comes from the nooks and crannies.