Our local Habitat affiliate has been given a house to refurbish. It’s in pretty good shape inside, but we’d like to add more insulation. We’re not sure on a couple of points…
Current walls are 2×4 with 3/4″ ship lap sheating on both sides. Plaster and lath on the inside. Currently insulated with blown-in rock wool. We’ve removed a few boards and the insulation looks good.
We’d like to put 3/4 foam insulation on the exterior and re-side with vinyl.
Should we seal all the joints around the foam board? Would that present moisture problems since there is no vapor barrier on the inside? Should we use house wrap or building paper? and where would it best be used (over or under the foam)?
Thanks!
Replies
Questions bring more questions.....
If the house has crawl space what's the insulation like underneath ??
If the house has old windows, what shape are they in ??
If the house has an attic, is it insulated ??
If the house has a chimney, is there a damper ??
I buy older houses and fix them up for rent and for sale. If you spend money insulating one part of the structure and not all of it, there is little if any, return on the investment. The foam backer to vinyl siding is good for the siding to retain its shape and form. I would only look at it from that view and not the insulating value. If you were to put a vapor barrier, you may be creating a moisture / condensation problem. Most older homes "breathed" and moved carbon dioxide out through the chimney, etc. Some new homes are so tight that they breed mold.... unless there is proper ventilation and it is used.
Of course, this is only "my" opinion and you may get others with a lot more technical info.
Good luck, Ken
In answer to your questions:
The windows will be replaced with new, engery efficient units.
The attic has 14" of fiberglass (6" between the ceiling joist and 8" batts laid across the joist). There's not much opportunity to add additional
The basement is uninsulated. The floor between the living area and basement is partially insulated (~30% of the floor area) with 8" batts.
The chimney has a damper by the furnace (oil, forced air)
OK... Go for it !!!
However, I do not think I would put any wrap or barrier between the vinyl or foam and the existing siding on the house... If the existing siding does not seem to have a moisture intrusion problem.. leave it alone.... If you put on a barrier, you would be creating another area to close in what is there and is working properly now...
Of course, that is "my" opinion and you have just got what you paid for....
Good luck,
Ken
I agree with Ken. Think you be farther ahead tightening up the structure against air infiltration and use good storms. Then add your insulation to the attic.
Half of good livin' is staying out of bad situations.
FHB did an article years ago about homemade Lawson trusses (relying on my memory here) anyway the were basically cheap trusses that added 1' of depth to the outside walls and were filled with "blown in insullation".
This also allows for a tyvec type paper on the outside. If you are thinking of redoing the exterior wall this may be worth looking into.
'Larsen' trusses. The article is in FH Annual Issue on Houses, Spring 1994, pp 78-81. About the house in Maine that didn't need a furnace. Also more in FHB #20, pp 35-37. At that time, they figured doing Larsen trusses added $15,262 to the cost, and saved them $8,700, most of that being from not installing a furnace (est at $7,200.) The house had no furnace, and the lowest recorded temperature was 40deg, before the owners had moved in.
Edited 12/9/2002 4:05:40 PM ET by martagon99
There goes the "cheap" theory