Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

attic insulation whats best?


ducati1212's Avatar
Member

Join Date: Jan 2012
Posts: 27
MA

04-30-12, 05:31 AM   #1  
attic insulation whats best?

Before next winter I need to better insultate my attic. My choices are either have blown in fiberglass type insulation onto the floor to beef up the 60 year old insulation thats there or what I think I want to do is spray foam the attic ceiling.

My question is whats the best option is spray foaming the ceiling (underside of roof) the sealing the attic the best solution? Its more expensive but ill spend the money if its worth it

 
Sponsored Links
drooplug's Avatar
Member

Join Date: Aug 2009
Posts: 4,940
NJ

04-30-12, 09:18 AM   #2  
I think spray foam on the roof deck is the best. Since unvented roofs are still a fairly new concept, not everyone likes it. They say it raises the temperature of the roof shingles and degrades them prematurely. There has been some study on this. I believe the results are that the shingles will get hotter, but not a significant amount to make a difference in the life of the shingle. If you do go this route, make sure the foam is closed cell and reaches down from the rafter bays to the top of the exterior walls. If you have soffit and ridge vents, you can opt to put the vent channels against the roof deck and spray foam over it to maintain ventilation against the roof deck. You can also remove the old insulation and spray foam the attic floor. If you have any ductwork or HVAC mechanicals in the attic, then going to the roof deck is the best option. It will improve the performance of your HVAC system.

 
ducati1212's Avatar
Member

Join Date: Jan 2012
Posts: 27
MA

04-30-12, 10:31 AM   #3  
I have a small attic there are no walls the roof deck comes right down to the floor. Its 46 x 25 in size about 4 feet tall max. I have 60 year old crappy fiberglass in the rafters that I was not going to touch. We get awful ice problems in winter so I thought the spray would be perfect.

I do have a concern that if the rood has a leak how do you detect it? it stays behind the foam and rots the wood? I cant get my head wrapped around that.

 
drooplug's Avatar
Member

Join Date: Aug 2009
Posts: 4,940
NJ

04-30-12, 10:41 AM   #4  
I was referring to the exterior walls below.

Leaks is another issue as well. I don't know to what extent damage can occur in that situation.

If you are getting ice dams and icicles, part of your issue is enough ventilation for that attic. I'm sure you still need to beef up your insulation, but if you don't go the spray foam route, you will want to air seal the attic floor and then put insulation on top. You will also want to increase the ventilation in that area as well.

 
ducati1212's Avatar
Member

Join Date: Jan 2012
Posts: 27
MA

04-30-12, 10:47 AM   #5  
I agree my 2 choices are

1) fix what I have which is probably more soffet vents and new blown in insulation

2) spray foam the roof deck.

Im trying to decide if spray foam is the newest super thing that I should do since im already going to do something. is it worth doing even though its 1000 ish more. I was leaning towards doing it. leaving what I have as is and spraying the roof deck.

there is no question what I have now fails on all levels

 
drooplug's Avatar
Member

Join Date: Aug 2009
Posts: 4,940
NJ

04-30-12, 01:15 PM   #6  
I plan on using spray foam for my roof when I eventually get to it. The advantages to closed cell spray foam are: double the R value per inch, air sealing, and it is a vapor barrier at thicknesses over 2". The air sealing is the biggest advantage and makes a big difference. The R-value per inch is an advantage if you don't have much space to work with. The vapor barrier part just makes things easier. If you have HVAC in your attic, then bringing your thermal barrier to the roof is even more important.

Spray foam is not a fad. It is pricey for sure, but it performs very well over other insulation types.

 
Search this Thread