Hello everyone ,
my question pertains to boosting the R value on a house , build with two by four exterior walls, that already has R 13 fiber glass insulation inside the walls. I am planning to remodel inside room by room, which among other things will include upgrading the electrical, plumbing and the like . Since I will remove the drywall to obtain access, what will be the implications of installing foil faced rigid insulation inside the house(conditioned space) against the existing fiberglass insulation and finishing the walls with the drywall. I know that is common practice to install rigid insulation on the exterior of walls, but since is a stucco exterior the cost of undergoing such a project would be too big.I live in northen part of California, with moderate winters, and medium to hot summers.
thanks in advance for any input.
ovi
Replies
ovi
It is not common practice to remove drywall for moderate electrical upgrades, nor to remove exterior drywall for plumbing changes as usually plumbing is avoided in outside walls in northern climates (perhaps not incl. n. cali).
You'd have to be really upgrading b/4 this would become a better price option.
My suggestion would be first an energy audit by a reputable firm or builder to see areas in need of adding insulation or concentrated air sealing.
Simple things like updating can light installation, adding insulation to the attic and perhaps the more extreme window upgrades could result in more bang for your buck. A little more information on type of stucco, age of house, attic insulation amount/r-value, quality of windows/doors............would be helpful.
thanks.
Just off the top of my head, installing drywall over insulation like that would be a really bad idea. How yould you keep the depth of your walls consistent?
I'd lean towards either inynene in the walls or strapping the walls and filling in between the strapping with rigid foam.
I've seen this done, and it's not a bad energy upgrade. Not only do you gain the R-value of the foam, you short circuit the thermal bridging of the studs. I say go for it. Except I'm not sure about the foil-faced foam. Where should the vapor retarder go in your climate? Inside or out? It doesn't sound like you're in a strong heating or cooling climate, so it may be a crap shoot. I'd be inclined to go with an eps foam because it would have a slightly higher vapor permeance than the FF. Also, you'll probably need to use extenders on your electrical boxes. No big deal, but you can't have the foam exposed to the inside of the boxes.
I've seen this done, and it's not a bad energy upgrade. Not only do you gain the R-value of the foam, you short circuit the thermal bridging of the studs. I say go for it. Except I'm not sure about the foil-faced foam. Where should the vapor retarder go in your climate? Inside or out? It doesn't sound like you're in a strong heating or cooling climate, so it may be a crap shoot. I'd be inclined to go with an eps foam because it would have a slightly higher vapor permeance than the FF. Also, you'll probably need to use extenders on your electrical boxes. No big deal, but you can't have the foam exposed to the inside of the boxes.
You leave a lot out of your post, and the devil is often in the details. So, I'll make a couple guesses ...
I'll guess the house was made before Johnson was president. I'll guess that there is no ground wire with your electric cables. I'll guess that there is sheathing - not just paper- on the outside of the house, and that the stucco is old.
Such houses typically have 'fire blocking' in every stud bay, about 4-ft. off the floor. The insulation is likely really 'rock wool,' and is pushed in at the studs, stapled to the outside sheathing.
You're likely to find major gaps in the insulation as you open the walls, as well as quite a bit of air leakage.
While your plan is not 'wrong,' and will do no harm, I suggest you reconsider.
A proper re-build would take full advantage, and significantly improve the house in many way. Alas, you may be better served using various contractors - even considering vacating the house and having it all done at once. Here are some points to consider:
1) First off, you can increase the stiffness of the wall, seal air leaks, and greatly improve your insulation by using spray foam. Such kits cost about $650 and will fill about 25-linear feet of wall with 3" of foam. I also advise coating the inside of the cavity - that is, the side against the outside wall- with an intumescent coating. You have enough trouble with wild fires; you might as well try to protect the foam!;
2) The horizontal fire blocks at the 4' level can be removed- run your drywall vertically;
3) The existing sheathing, if it is made of boards, adds little stiffness to the wall. Consider facing the inside of the wall with 3/4" OSB, then applying your drywall on top of that; finally,
4) Remember that both plumbing and electrical codes have changed considerably since the house was built. You'll want to get the "Code Check" book and bring it all up to date. This will mean different materials, more outlets, and more vents.
A couple points of question
R13 fibreglas wasn't around b/4 Johnson was president. The original poster did mention fibreglass, so unless he's wrong-it's not rock wool.
Maybe I'm ignorant of California building over the yrs, but blocking at 4' is not common practice.
So if the house isn't old, it's a bit of a stretch to suggest that plumbing/codes are way out of date or even in need of bringing up to date.
of course the above implies the poster comes back and fills in the numerous blanks.
thanks.