# Insulating House with Block Walls--revisited



## rmcfall (Aug 27, 2007)

I've got a few more questions about insulating the walls of my home and thought it'd be easier if I started a new thread.  My question is about how to insulate the block walls of the living area of my home, NOT the block walls in my basement.  

From the previous thread, moisture seemed to be a concern when insulating block walls, so spray foam seemed like the way to go.  However, spray foam is expensive and if moisture isn't an issue, then is it really necessary?  I can understand how moisture is a concern with basement walls, but is it really a concern with the block walls of the living areas of my house since those areas are above ground?   If moisture isn't a concern, then it seems like building new insulated stud walls just inside of the block walls would be the easiest and most economical.  The other inexpensive option would be foam board in between furring strips, but the R value of these boards isn't much.   What do you all think?  Do I really need to worry about moisture and mold if I use regular insulation inside stud walls built next to these block walls?


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## wg_bent (Aug 28, 2007)

Yes, you do.  The dew point will be inside the walls somewhere.  IN the winter, you want to prevent warm interior moist air from getting to the outside.  The moisture collects and can cause wall damage.  In the summer the reverse happens.  Warm moist outside air infiltrates to the inside and hits a dew point inside the walls.  This is particularly problematic with insulations like fiber glass and cellulose, but both can be managed by adding a backing layer like a backed fiberglass or a plastic layer. With a foam board like insul-pink, there is almost no air movement, so the effect is minimized.  With a spray foam, there is NO air movement, so the problem is eliminated.  The other issue with fiberglass is that with even the smallest of air movement, the effectiveness of the insulation is reduced to something like 10% effective.  In this way the foam products outperform the fiberglass.  If you can truely eliminate the air movement (Johns manville's (sp?) encased bats do a good job of this) then the fiberglass is a nice product.  If you feel air coming through your plugs at all... I wouldn't use fiberglass bats with the paper backing.


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## rmcfall (Aug 28, 2007)

Thanks for the response.  Did your setup of using 2" insulpink followed by studs with fiberglass bats work out OK in your basement?  That is, did the insulpink provide a sufficient moisture barrier?  Perhaps I could do the same with the block walls along my main living area. Again, the walls are brick, block, and then plaster applied directly to the block.  There are no noticeable air leaks.  I am tempted to follow what you did, but I hate to lose that much wall space.  In my basement it will be a non-issue, but as far the main living areas of my house it seems like the area lost would start to add up (especially for some of the smaller bedrooms).  How much do you think adding the fiberglass to the insulpink helps?  The Owens Corning website says the insulpink comes in 1 1/2" depths at an R-Value of 7.5.  Would applying just the insulpink offer only a negligible improvement compared to using both the insulpink and fiberglass bats?  

BTW....this link talks about reflective insulation at an R of 14.5.  Is that number believable?      Sounds too good to be true...

http://www.insulation4less.com/prodex_Ffmf.asp


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## wg_bent (Aug 28, 2007)

Actually I must correct what I put in... I used Foamular 2".  Same stuff as the insulpink, just a slightly different format for install.  Plus the 2" is R10 total.  I drylocked the walls, then did the Foamular, then R13.  The basement is a LOT  dryer and more comfortable than it was.  It can be heated with a small electric heater (baseboard is coming soon) easily.  Honestly, I probably went overboard somewhat, but I sure with my hole house was insulated this way.  With cinderblock walls and sheet rock.. in total it's R25 or so, plus with the solid insulation board, There's no drafts.

I'd do it that way again in a heartbeat.

Spend time reading this site:  http://www.buildingscienceconsulting.com/resources/resources.htm


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## rmcfall (Aug 28, 2007)

Thanks for the link...lots of information there.  What is interesting is that they mention using a combination of rigid foam board and fiberglass to insulate basement walls, but they only depict using rigid foam board for the masonry walls of the main level of a house.  I wonder if they consider the addition of fiberglass at this level of a house to be overkill?   Any thoughts?  

Something else that is interesting is that they say to avoid metal furring or "hat" channels due to thermal bridging and impermeability.  They also specify that pressure treated studs are preferred to metal studs when using fiberglass because the metal is conductive and is prone to condensation. 

Lots of good information there.   Thanks again.


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## wg_bent (Aug 29, 2007)

Today code calls for R19 walls.  It's my belief that it should be double that.  I have a friend who has a home that has 6" of foam pumped in followed by 2" of foil backed rigid board then sheet rock.  Total is like R40 walls.  His house requires about a cord and a half to heat with a VC Defiant.  

I consider that house well insulated.  He's very anal about plugging all leaks, but it pays off.  The house is very comfortable in all seasons.

For what your doing, you might get away with 2 layers of the foam board... but beware... it ain't cheap!


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## elkimmeg (Aug 29, 2007)

> I wouldn’t use fiberglass bats with the paper backing.



It has been proven the Al foil faced batts loose there reflecvive value in less than a year. A film  collects on the facing and causes this result.

I still say the basement block/concrete walls should be damp proofed with 2 coats of Drylock before applying any product to them

Unfaced bats  still require  a vapor proof barrier towards the living space.. The spray foam myth ther r- value is derived fro the full 4" unfortunately 2/4's are 3.5" and the foam at 3.5" does not exceed R 15 fiberglass dose. In the insdustry each industry is promoting the merits of its producte and testing the other to find faults

 then there are major points that allowing a home to breath has merits,  foam can not do this  Then the arguement the air quality is better in a fiberglass insulated home. the counter if not installed properly fiberglass does not achieve its true R- value  I got news many products do not ppreform properly unless instlled that way

 I can point to over 100 homes in my town the past 3 years earning energy star approval using fiberglass insulation Each product has issues one being cost, properly done both products should preform as they should.


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## rmcfall (Aug 29, 2007)

Hey Elk.  What about damp-proofing my masonry walls that aren't in the basement and are on the main level of my house.   These plaster walls are painted.   I didn't think Drylock could be applied to painted walls....??




			
				elkimmeg said:
			
		

> > I wouldn’t use fiberglass bats with the paper backing.
> 
> 
> 
> ...


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## rmcfall (Aug 29, 2007)

Wow...that's quite an insulated wall your friend has.  How large is his house and what part of the country is it in?  Only a cord and a half in a Defiant...that's impressive...




			
				Warren said:
			
		

> Today code calls for R19 walls.  It's my belief that it should be double that.  I have a friend who has a home that has 6" of foam pumped in followed by 2" of foil backed rigid board then sheet rock.  Total is like R40 walls.  His house requires about a cord and a half to heat with a VC Defiant.
> 
> I consider that house well insulated.  He's very anal about plugging all leaks, but it pays off.  The house is very comfortable in all seasons.
> 
> For what your doing, you might get away with 2 layers of the foam board... but beware... it ain't cheap!


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## elkimmeg (Aug 29, 2007)

I was refering drylock to walls that have ground contact foundation walls.  Warran has it right prevent moisture from comming threw the block foundation walls and vapor barrier prevents inside moisture from  it pentrating into the wall  Really I don't know about paint over drylock


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## wg_bent (Aug 29, 2007)

rmcfall said:
			
		

> Wow...that's quite an insulated wall your friend has.  How large is his house and what part of the country is it in?  Only a cord and a half in a Defiant...that's impressive...
> 
> 
> 
> ...



Just down the road from me in Poughkeepsie.  House is about 1400 sqft.   (but... he just doubled it... I'll have to see how well the new addition does on the heating)

Yeah, he's also got enough solar to run the meter backwards almost all year, plus the house is an active solar design with massive heat storage below the home.  It's really amazing how over engineered it is.


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## rmcfall (Aug 29, 2007)

That's impressive.  In terms of the 8" of insulation he has, was that done when the house was built or afterwards.  If afterwards, how do those large window sills look?


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## wg_bent (Aug 30, 2007)

It looks great.  The house has a post and frame look inside (it's fake) a Large fireplace (the winter air conditioner) and a very open floor plan. The only two doors in the whole place are the bathroom and one bedroom.  Then came the addition.  Doubled the size of the house.  I haven't seen it finished yet.  He was working on it all summer after his contractor bailed on him.


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## coldinny (Nov 19, 2007)

I am also in Dutchess.  I was poking around my basement today (something one should never do) and discovered drafts coming up from my foundation through the cinder block walls.  
the cinder block walls have holes which were partially blocked by old fiberglass batting.  and the walls do not go all the way to the floorboards above.

 do you have any suggestions for the best way of dealing with this nasty surprise - insullatio and heatwise?


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