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Old 08-23-11, 09:32 AM   #1
wendortb
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Default 1.5 story house indiana (long)

My wife and I live in a 1.5 story house in Indiana that was built in 1994. The insulation isn't the greatest in several locations and I see some room for improvements. Whatever I do I have to have a good ROI or the wife won't approve it. I am trying to come up with a plan off attack.

The house:

1500 sq ft 28x36 rectangle house, 2nd story has cathedral ceilings and knee walls. I hit my head all the time on the cathedral ceilings.
Slab foundation with 1 concrete block as the bottom part of the wall. Sills sit on top of this block.
2x6 walls with R11 faced fiberglass and 1" foam sheathing and vinyl siding.
2x8 cathedral ceiling on 2nd floor with R19 faced fiberglass that allows air to pass through them for a vented roof.
2x4 knee walls on 2nd floor with faced r11 fiberglass
Eave and ridge vents along entire length of house.

80% propane furnace with ductwork that runs from downstairs, into unconditioned attic(behind knee wall) then splits behind knee wall with metal duct and has insulated flexible ducts coming off of the trunk.
Central a/c is a 10 seer unit.


Things I have done:
Sealed alot of the ductwork that I could reach with mastic and metal duct tape. I can tell I still have a negative pressure on the house but can't find those leaks.
Added metal roof and fanfold insulation on top of existing shingled roof. (I wish I would have added 1-2" foam at that time)
Sprayed cellulose insulation behind knee walls to add insulation to ducts and approx 6' of 1st floor ceiling. (I hoped this would also slow the air flow from under the knee wall, but then I read it won't stop much air being loose fill.)
Caulked/touch foamed - outlet boxes and windows and doors.




I have been using the builditsolar insulation upgrade calculator to figure out what upgrades will pay for themselves in a relatively short time.

Areas for improvement:
1. Concrete block on top of concrete slab: According the what I have read, this block is only an r1 and there is no insulation, just drywall covering it. According to my calculations, I should make my money back in 1-2 years by insulating this. I was thinking about Insulated panels over the block, butted up against the existing insulation, and digging down into the ground to get a little below ground level with them. The block is exposed 6" all the way around with the foundation exposed another 6" in most spots.

2. Walls: The 2x6 walls seem like they are being wasted with so little fiberglass in them (r11 + r5 foam). I thought about having someone blow cellulose in them by removing the vinyl siding, drilling holes in the foam, and dense packing. If my calculations are correct, I should be able to make the money back on this in 3-5 years and save $100 a year on my heating bill. Later, when we redo the siding, I can add another inch or 2 of foam board on the outside to further insulate the walls.

3. Cathedral Ceiling: R19 ceiling when they call for R49 is quite a difference. Also, from what I have read the fiberglass is losing most of it's heat because the attic ventilation is going right through this fiberglass. I have looked at several options and am thinking about either
1" air space/1" foam/cellulose filled/1" foam over rafters/drywall
OR
1" air space/3 layers of 2" foam/ 1" foam over rafters/drywall.
Closed cell spray foam would get me closer to r49, but from what I have seen it would be 5K or more to have this done and I would never make the money back.
The problem with convincing the wife on this one is i technically have r19 and would be upgrading to r28.9 with cellulose/ r36 with rigid foam. Using the calculator I would only save around 70/100 per year and it would cost 1300/2500 respectively. The payback becomes 27 years/42 years. That is a long payback time to convince the wife for such a big project.
Before the recent upgrades, I would get ice damming and a lot of snow melt on the upper portion of the roof. Now with the metal roof, the snow slides off before I can tell what it is doing.
Are the air leaks enough to justify doing this first?


4. Under Knee Wall:

I believe this is one of my biggest air leaks and is the hardest for me to seal. I have thought about just enclosing this area the same way I do when i do the cathedral ceiling and just insulating the roof, instead of the ceilings. This would put these holes and the ductwork in a conditioned/sealed space.

My other option to stop the air leaks is to cut foam board and stick in these holes. Accessing them would be a pain because that means either cutting holes in my 1st floor ceiling or trying to work around the duct work that is right behind the 1 knee wall.

5. Heating and a/c unit: I have thought about replacing my furnace & a/c in a few years with a geothermal unit. I figure my energy costs will be cut in half and it would pay for itself in approx 15 years. According to what I have read, the geothermal unit will last longer and be more energy efficient. The only downfall is cost. I'm estimating 15K for install (guessing). Air source heat pump wouldn't work as well because of the cold weather that we get.

Current electric rates are $0.11/kwh and propane is $2.65/gallon (last year propane was 2.29/gallon). With the improvements I have made already, my last month's electric bill(a/c) is $50 less than last years.

Thanks,
Travis

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Old 08-23-11, 10:58 AM   #2
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I would give up entirely on trying to fiddle with the knee walls and just bring that space into the conditioned area. It's nearly impossible to make those walls air tight. Another thing you could do is have a hot roof. It would take some work but you could do it. Then you could dense pack those rafter bays and give the bird to the high density spray foam people who ask you for 5K for bringing more petrochemicals into your house.
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Old 08-23-11, 11:21 AM   #3
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I wasn't sure if I could do a hot roof. Looking at some case study on unvented roofs, it looks like for my area (closest is chicago with light metal roof) I would need 2" closed cell spray foam to keep the moisture from collecting on the underside of the roof. Cellulose would gather too much moisture according to that.

If I am wrong, I would love to hear so, I could get an r26 cellulose without any rigid foam and not have to bring my ceiling lower, or with rigid foam i could get R31.

The only other option I have seen for an unvented roof is to have 1/3 of the insulation(rigid foam) on top of the roof decking. I don't have anywhere near this and it is too difficult to add.
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Old 08-23-11, 11:35 AM   #4
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It's too bad you already had that roof put on. Otherwise you could put 4" of foam up there and seal it all up. No matter what you do I suggest you bring the crawlspace behind the kneewall into the thermal envelope.
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Old 08-23-11, 02:35 PM   #5
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If I knew then what I know now. I was in a hurry to get the metal roof on at the time because the time for the federal rebate was running out. I wasn't thinking about insulation at the time.

Now that I look at it, it would have been awesome to throw some rigid foam up there.
Unless someone tells me different, I will have to keep the 1" venting and just lose the R through the roof.
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Old 08-23-11, 04:32 PM   #6
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Travis,

I'd suggest spending some time here - Home Energy Saver. It will take a while to enter all of the data, but you will get a better overall picture of your home. The Home Energy Saver also has pretty detailed ROI info on a variety of possible insulation / efficiency upgrades.

It's very frustrating to look back on a recent project and realize what you would have done differently if you had only known a little more. All I can say is, do the different ROI calcs NOW and you'll know how to approach any new projects.

FWIW,
Tim
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Old 08-23-11, 05:34 PM   #7
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So that spray foam quote was just for the portion of the roof which is not accessible? Do you have an attic of any kind? Here are my thoughts: First things first. Dig around your perimeter and plant some XPS to insulate the slab, wall and whatever block is above grade. This is a fairly simple DIY but it is labor intensive with all the digging. Don't skimp on the foam. I would put 4" all the way down and more from 2' below grade up to your wall. Always think at least R 40 for walls above grade. And air seal the transition well after placing a termite barrier on top of the XPS. For the space behind the kneewall I'd get some kind of board insulation and cover every surface that meets the outside and air seal it all. If you use foil faced polyiso you can tape everything with foil tape. If you use recycled polysio (much cheaper, better R value) then you would just seal it all up with 1 part foam. This will create a gap for your ventilated roof the depth of your bay. You could cut up pieces of foam board to fit the bays, place them in leaving 2" between them and the roof deck and foam them in place reclaiming some of that bay space for insulation. Alternatively you could put insulmesh in the bays leaving 3" or so between it and the roof deck, screw foam to the inside and then dense pack through the foam. Myself, if I were in your position I'd block off a space for the vent, using sheetrock and 1 part foam to make it air tight and then truss out into the space to create a 12" cavity for cellulose. I personally dislike using or living in a house full of foam. After I had everything done before the cellulose was packed I'd improvise a blowerdoor in the door in the kneewall, pressurize the space and look for air leaks with a smoke pen or incense stick and seal them up with extreme prejudice. As for the portion of the roof behind walls I think I'd probably wait, save my pennies, sweet talk my wife with stories of houses that don't need heat or AC and then call in the high density spray foam people. Sucks. They have their place but I'd rather it wasn't anywhere near me. Unless you can outsulate you really are trapped by the tiny space you have to work with. If you plan to keep this house you have to think about more than just ROI. A well sealed and insulated house is just plain more comfortable when you are separating it from the elements. In the winter if you set the thermostat to 75 the house doesn’t feel like it does with the windows open on a 75 degree day…… unless it’s well insulated and air sealed. Then you need to go out the door to feel the difference. It’s about comfort. Not only financial comfort but also physical comfort on a level that most people have never experienced. Everyone’s idea of outside temperatures is different from their idea of what’s created by the temperature on the thermostat.
I have tried to take the crawl space behind a kneewall out of the thermal boundary several times and it has never worked well, it’s labor intensive and it sucks. You have to drill into the floor right by the wall, stuff a feed bag in there, push it way back behind the wall with the hose and dense pack it hoping it creates an air seal. 0.o Dense packing floors is lame any way since you only get minimal insulation in there. And then you have to pray to the air sealing gods that you can actually seal up the knee wall itself (which you can’t). You have to pull up your carpet next to the wall and caulk the trim by the floor using a bastadrized version of the Airtight Drywall Approach. I look at all attics and attic like space as a fantastic opportunity for insulation storage. Just pile it in. Cellulose is cheap and it doesn’t really cost much to have to blown in if it’s not an exterior retrofit. If it’s a loose blow you can DIY with a machine Home Depot will just let you borrow for free. If you have an attic of any kind you can crawl in there with a hose, block off 2” for ventilation with cardboard and Tyvek tape and absolutely fill it with cellulose. No attic = spray foam, $ and petrochemicals. Not to mention all of the other concerns associated with spray foam vs. cellulose. Here’s a rule of thumb I’ve developed recently: If you’re talking to an auditor or contractor or anyone and they say that a certain amount of insulation or air sealing is “enough” you are talking to the wrong person. Enough for what? Get a 1 part foam gun and ask for a case of foam cans for Father’s Day. Foam everything from outside the thermal boundary, but keep the foam out of the light or it’ll go bad. Once cured the foam deteriorates with light contact. You can tell because it turns yellow.

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