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bfan781 05-17-2010 10:34 AM

looking for Serious advice and Help on Insulation
I love this forum and have gained so much knowledge and insight on projects. I always feel that the advice and opinions are true and accurate and not from contractors who are trying to sell you more their product to jack up the price. I am doing everything myself. So I guess this is more of advice and what would you do?
I am trying to figure out the best/most cost effective way to insulate a remodel project i'm doing. The major issue is that all the framing is 2X6's. There are a number of options and possibilites to go with, and I am stuck as to what to do. Bascially, its a second floor redo with a shed dormer on the back and a kneewall running the lenght of the front. I have done so much research and now just need some advice. I plan to at the "minimum" use spray foam from the lenght of the shed dormer down to the kneewall to avoid venting and also achieve a higher R-value. I have gotten price to spray the whole roof line (both sides of the kneewall) as well as the exterior walls, but it is very costly and we aren't planning on staying in the house to long. But it is a lot easier because they come in and in a day the insulation is done. I do not know if it worth investing that much money when I will not be there long term we are moving in a few years. The kneewall space we want to use for storage. If I do not spray the entire roofline, I would have to most likely build up the kneewall floor to allow for more blown in. Much much dense blown in can you get in say 8"? for the knee wall I would either use fiberglass or blow inand then can i put foam board on the back side of the kneewall to make it more effiecent?
Is it pointless to do the whole roofline in foam, and then do the exterior walls in fiberglass/blown in? Am I losing alot of the effiecency of the foam?
Basically, I can do this a few ways or after I built everything up and get the other insulation in place would it have not been that far off to just spray everything?
1) spray foam everything walls/roof etc- Costly and we are not staying to long in the house to see the rewards.
2) spray down to the kneewall, insulate kneewall and inside kneewall floor with fiberglass/blow in - more work, would have to build up kneewall floor to accomadate more material and put down plywood for storage.
3) Spray entire roofline and use fiberglass/blown in on the exterior walls. Kneewall won't need to be insulated?
What are some ideas and opinion? Really need help on this one. IS the dense blown in expensive?

RoyalAcresRod 05-17-2010 03:41 PM

First of all...please put your location up...answers can depend on the climate in your area! What is recoemended and/or minimum R-value for ceilings in your area? Can you get to that value w/o furring out the rafters? (non-foam)

And it seems to me that to make a logical decision you'll need to know the cost of the alternative to foaming the whole area.

Too, you mention that you'll not be in the home long-term. Although more and more folks are seems to me that if you're not going to be in the home long enough to recoup the extra $$$$ spent, few people are going to pay extra for this add'l insulation. It may help MAKE the sale, but not necessarily add value.

The appraisal of your home's value is going to depend or comparatively priced homes in your area, and/or X$/ square foot.


bfan781 05-17-2010 06:32 PM

Sorry about that. I am in Boston. Furring out the rafters is impossible because the headroom is already tight. The R value is 38 but I can not get that regardless and don't have to either. Thats what kind of pushed me towards the foam in the first place. Before there was R19 of fiberglass, I feel to get and R30 with foam will be such an upgrade. Question is what to too with the rest of the area.
Let me ask this, any idea what the dense blown in costs? I can't seem to find it in the box stores, what is the R value per inch of that? If I go with foam on the main roofline of the living space and treat the other side as attic, will foamboard on the back side of the kneewall help stop the heat/cold transfer between the two spaces? Any other input?

seeyou 05-17-2010 07:05 PM

any idea what the dense blown in costs?

Are DIYing this or hiring it out. When you say "dense blown in", are you referring to cellulose? Cellulose probably gives the best return on investment in a lot of cases.

If so, Google "Mooney Wall".

Another option might be foam board if you're demo-ing the plaster/drywall.

RoyalAcresRod 05-18-2010 07:37 PM

I really can't comment, here in OK, on Massachusetts costs of having dense pack cellulose installed, even though I grew up there! Time to make some calls to local insulation companies. I can tell you that it would be rare to find a DIY blower for installation...the equipment involved uses much higher pressure than what is spec'd in the blowers typically rented or given for use when you buy X amount of material.

Now, an intermediate option might be to install rigid insulation board, either XPS or could cut them pretty close to your actual dimensions, them use canned foam to make final seal. Also, that's an excellent reason to buy a Hilti foam more partial wasted cans remaining.

Now, you'll have to use the best-R-value-per-inch polyisocyanurate, and not vent the rafter bay, to get close to R-36, if my math is correct. Of course, I understand from a previous post that you're OK with that.

You're best bet, again, is to get bids for what you want to do, and gather material costs for DIY, to make the decision best for you. The best solution might be mixture of both.

PS One thing to remember is that for a small job such as this, you'll pay more per square ft, or whatever the measurement is, than for a larger job, for the installer has to set up, tear down, and clean up the same as for a large job....


bfan781 05-19-2010 09:56 AM

So are u saying to stack up foam boards to fill the entire rafter bay? Is that allowable by code? Do u also not need to vent the roof with this method? Has anyone had issues with this method?

RoyalAcresRod 05-19-2010 11:02 AM

I'm a big fan of ensuring that the rafter bays are ventilated. I have ensured ventilation of rafter bays in cathedral ceilings in two similar ways, depending on the available depth.

In the first case, I nailed 1X2s to the roof side of rafters (nail to rafter), then cut and fit foil-faced polyiso board to fit inside the rafter bay using cap nails. This gave an approx 1.5 inch "vent chute) area behind in board. I then filled the rest of the bay with foam board.

In another instance i purchased the pre-made light foam vent chutes, and stapled them up the rafter bay, overlapping slightlly (then come in about 4 foot length), then installed insulation.

I realize your headroom is tight....but even furring out 1 inch will give you an extra R-6.5 if using polyisocyanurate.

It all comes down to either paying now for more value per inch with XPS or polyiso, or paying later in HVAC costs. Of course, as in all things in life, there are tradeoffs in every decision. Only you can decide if the payback period of the add'l costs in using premium material is worth it, depending on the costs, the length of time you inside to stay, and the increased (doubtful) sales price when you decide to move on.


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