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need help with adding insulation to attic

armchairdiyer's Avatar

Join Date: Dec 2007
Posts: 2

12-12-07, 12:31 AM   #1  
need help with adding insulation to attic


been lurking from some time, time to get out of the armchair now...

I am on a quest to increase the energy efficiency of our old house. I want to add insulation in the attic space but I am unsure what is the best way to go.

Some background information. I am attaching a picture that will hopefully clarify the layout.
  • The house was build in 1950. It is located in NJ.
  • Currently there are fiberglass batts in the yellow and green areas, about 4" thick, compressed in several places.
  • The kraft paper has been installed facing the attic (i.e. the wrong side - not facing the room). It is torn pretty much everywhere, so it must be almost ineffective as vapor retardant at this point.
  • There are no soffits - hence no soffit vents. There is a continuous ridge vent and gable vents on both sides, plus a small attic fan.
  • The top part of the attic is very low, about 2' only at the highest spot. I can barely crawl there.

My plan is to reach the recommended R49 grade by:
1. blow cellulose in the green areas since it is hard to get there.
2. add additional fiberglass batts in the green area
I wouldn't want to remove the existing insulation because it is very hard to get into the upper part of the attic.

Now the questions:
  1. Does the plan sound reasonable?
  2. Eventually I want to add a whole house fan. Will it blow the cellulose away? Would it be to use fiberglass batts in the upper area too?
  3. Can I keep the existing insulation of should I get rid of it?
  4. If I keep it, what do I do with the vapor barrier? The current one is installed incorrectly, and, likely, it is not effective anyway. Adding another one on top of the existing one is wrong according to everything I read.
  5. Do I need to add rafter vents even though there are no soffit vents? Again, the space is very tight and I would like to avoid squeezing myself in there.

Any suggestion is welcome.


Picture not in scale

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chfite's Avatar

Join Date: Nov 2001
Posts: 9,483

12-12-07, 05:10 AM   #2  
Some points to consider:

The yellow area should still have venting from bottom to top after all is complete.

The attic ventilator is probably useless in conjunction with the ridge vent and gable end vents.

It will likely be more successful to blow cellulose rather than to place batts. The loose material will close and fill areas that you won't be able to reach with batts. The skill and ability of an installer can be impressive. I found that a contractor could install blown insulation cheaper than I could even buy the materials.

It makes sense to leave the existing insulation. You simply add to it with the blown insulation to achieve the desired thickness.

Given the amount of paint on the walls and ceilings in 50 years, the vapor barrier on insulation is probably irrelevant.

Installing soffit vents in a house with closed soffits would be a task of impressive magnitude. If the total ventilation area provided by the gable vents and the ridge vent is sufficient, it seems difficult to justify adding soffit vents in your case.

A whole house fan won't blow away the insulation.

Hope this helps.

armchairdiyer's Avatar

Join Date: Dec 2007
Posts: 2

12-12-07, 09:38 AM   #3  
thanks for the reply, chfite. You pretty much answered to all my questions.

How can I know if I have enough ventilation in the attic? It's a good 15 degrees above the outside temperature both in hot and cold weather. I guess that's sign of poor ventilation, isn't it? Then again, the area above the bedroom is so narrow that it gets warmed up easily.

I was thinking of doing the job myself, but maybe I should check first with some contractors. However, being that this is NJ, every job comes with a hefty mark-up compared to other parts of the country.

d00bs's Avatar

Join Date: Sep 2005
Posts: 195

12-12-07, 10:19 AM   #4  
Read these two files on how the green area should be insukated http://www.dom.com/customer/efficien...er_garages.pdf
and http://www.eere.energy.gov/buildings...pdfs/26447.pdf

One of them talks specifically about a room over a garage but these 2 options are how a side attic is insulated.

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