buckeyefarmer
Epic Contributor
Looks good.
New House Build in the Country!!!
- Thread starter justinramani
- Start date
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Justin if there is any way to swing the spray foam try to do it. You can get to the attic later but now is your only chance to do the exterior walls. I've made some adjustments to zoning dampers and spent this evening monitoring HVAC run times from my laptop. Heat is set at 70 degrees for all zones, basement off. From 8:30 this evening (outside temp 35 degrees) until 12:30am (31 degrees outside temp) I have a total run time of 53 minutes heating our 1st and 2nd floor with a total of 3,900 sq/ft. That's with no solar gain.
Here's one more example. The below pic is an outside wall with 2-1/2" of closed cell spray foam. Under the foam is OSB sheeting and vinyl siding. Outside air temp is 29 degrees when pic was taken. Inside air temp was 66 degrees.
I do understand how hard it is to stay on budget though, let alone find several thousand dollars for something extra. At least seal the best you can with vapor barrier and make sure you blower test.
OP
justinramani
Gold Member
How much better is closed cell vs. Open cell?
EddieWalker
Epic Contributor
Closed cell will give you a much higher R value which is very important for small spaces, like the depth of your rafters. Open cell is a lot cheaper, so you can reach an R value for a lot less money if you have the space.
Closed cell means that each little bubble is water tight. It keeps out moisture, it's hard to the touch, and for docks, it floats.
Open cell absorbs water, it's soft to the touch, and when it gets wet mold grows. It is very bad for metal roofs, or most roofs when sprayed right on the roof. Condensation will form under the roof, soak into the open cell, and mold will grow. It just gets worse from there.
Closed cell means that each little bubble is water tight. It keeps out moisture, it's hard to the touch, and for docks, it floats.
Open cell absorbs water, it's soft to the touch, and when it gets wet mold grows. It is very bad for metal roofs, or most roofs when sprayed right on the roof. Condensation will form under the roof, soak into the open cell, and mold will grow. It just gets worse from there.
KennyG
Elite Member
Reading all this about insulation and sealing the house raises the question of ventilation. When you seal the house so completely, you will get build up of pollutants inside the house. With these modern building techniques, you should also have a heat recovery ventilation system.
Hate to throw out cost increases, but if you don't already have that in the plans, at least try to get the inlet/outlets built in so you can add it later if you need it. Depending on the size and design of the ventilation units they can cost from $1000 to $5000 and have relatively low operating costs.
I added one when I remodeled and re-insulated the house. It's made a lot of difference in air quality and humidity control.
Hate to throw out cost increases, but if you don't already have that in the plans, at least try to get the inlet/outlets built in so you can add it later if you need it. Depending on the size and design of the ventilation units they can cost from $1000 to $5000 and have relatively low operating costs.
I added one when I remodeled and re-insulated the house. It's made a lot of difference in air quality and humidity control.
EddieWalker
Epic Contributor
I have a friend who build a 1,200 square foot weekender home that he and his wife are now living in while debating on where they want to build their next permanent home. They spent as much as possible on that place, including closed cell insulation on all the exterior walls and ceiling. Their electric bill is never over $40 a month. But the funny thing is that it's so air tight that they cannot get a good fire going in their fireplace unless they open a window. I don't know if or why they didn't put an air vent into the fireplace, this is just what he told me.
The first time I heard about whole house envelopes and not having any venting was in a magazine article in Fine Home Building right after the Southern California Fire Storm that burned thousands of homes. There was one house left standing in perfect condition on the side of a hill with hundreds of houses all around it burned down to the foundation. It's a very powerful picture.
The owner of that house was interviewed for the article. He said that when he built the house, he wanted to do a few things to protect it from a fire. He doubled the thickness of the stucco on the walls and he did not have any vents into the attic. He also used clay tiles for the roof. Basically he built a house that wouldn't burn, or allow the heat into the house if there was a fire. I think he did something special with the windows too, but I can't recall what he used there. What I do remember was how he felt that it was very important not to have those vents to allow the fire to get into the roof area of his house.
In other articles about entire house encapsulation, it's pretty clear that there is a good argument for heating and cooling the entire outside shell of the house, including the attic space compared to the traditional method of insulating the ceiling. Since then, the R value standard for attic space has gone from R30 to R60. In my opinion, R60 reached with blow in insulation is much more cost effective the foam. It costs less to install, and the long term energy savings is the same, so you never make back your investment going with foam if you can use blown in insulation to reach R60.
If you cannot get to R60 with blown in insulation, then foam can become a good alternative. This is where the math gets tricky.
The first time I heard about whole house envelopes and not having any venting was in a magazine article in Fine Home Building right after the Southern California Fire Storm that burned thousands of homes. There was one house left standing in perfect condition on the side of a hill with hundreds of houses all around it burned down to the foundation. It's a very powerful picture.
The owner of that house was interviewed for the article. He said that when he built the house, he wanted to do a few things to protect it from a fire. He doubled the thickness of the stucco on the walls and he did not have any vents into the attic. He also used clay tiles for the roof. Basically he built a house that wouldn't burn, or allow the heat into the house if there was a fire. I think he did something special with the windows too, but I can't recall what he used there. What I do remember was how he felt that it was very important not to have those vents to allow the fire to get into the roof area of his house.
In other articles about entire house encapsulation, it's pretty clear that there is a good argument for heating and cooling the entire outside shell of the house, including the attic space compared to the traditional method of insulating the ceiling. Since then, the R value standard for attic space has gone from R30 to R60. In my opinion, R60 reached with blow in insulation is much more cost effective the foam. It costs less to install, and the long term energy savings is the same, so you never make back your investment going with foam if you can use blown in insulation to reach R60.
If you cannot get to R60 with blown in insulation, then foam can become a good alternative. This is where the math gets tricky.
Good point Kenny. We currently ventilate with three kids. When we trade them in we have our system setup to add ventilation at a later time. Your HVAC load will also be less with foam. The smaller HVAC system may or may not offset the ventilation recovery system.
buckeyefarmer
Epic Contributor
As a comparison, during those same 4 hr times last night, my upstairs geo unit ran 1.8 hrs and downstairs ran 2.09 hrs. Outside temp went from 36.2 to 33.6. I have all batt insulation, and too much air leakage around the batts. R30 ceilings.
Mine set at 67.
OP
justinramani
Gold Member
Jk96-
Thanks for the stats - it sounds like your house has the right set-up! I'm going to broach the subject with the builder today and see what he says. I've been making a lot of changes lately, luckily he has taken it all in stride. I'll provide an update when I know more about the additional costs. All of this feedback is great! I really appreciate everyone's advice.
Not a problem. It's easy for us to sit here and spend your money. You have to do what makes sense for you. Either way seal the leaks before you rock and the time taken to do it right will pay off.