R-values in a mid '70s house

[ironhat]

I'll be removing the T1-11 and replacing it with Hardiboard. While I have the walls down to the studs I would like to improve the R factor in the walls. Can anyone comment or steer me to someone who can regarding the method, materials and feasability of such a project? I've had suggestions from adding on to the studs to the equivalent of 2"x6" and top off the current insulation to removing the old and less efficient insulation and spraying in some cellulose, top off and over the studs with rigid foamboard with a reflective barrier and attach the cement board over that. I'm leary of hanging the top layer to foam - you know, gravity.

TIA!

[chopnhack]

I guess alot of what you can do will be limited to how much overhang you have and where the soffit openings (if any) are placed. Building out the wall is a great way to increase your R-value, but depending on how many openings, it might be too much work/dollars. I'm sure others here may have done this so, soon they will chime in.

[master53yoda]

Most likely you have R11 in the 70s 2x4 studding can only go to R13 max.

unless there is another reason for removing the t1-11 siding . If it was me I would probabley consider putting a 1" or 1 1/2 faced high density foam board over the t1-11 leaving the t-11 there for structural purposes, as well as leaving the existing insulation alone, and then putting the siding over the foam board with glue and fasteners long enough to get into the t1-11. the Foam board will also generate an infiltration barrier which in a 70s house would gain you more then adding the insulation would. I would also look at upgrading the windows if that isn't in you process already. Your walls would end up being about as thick as 2x6 consturction with very similiar insulation values. Then raising the attic insulation to 10 to 12" and insulating any crawl space would give you a very well insulated house. Bear in mind that if the house is extreamly tight you may need to add mechanical ventilation in order to control moisture levels inside the house and provide sufficient clean air. The house now probably leaks 3 to 5 air changes per hour and what i've sugested above could bring it lower then 1/2 hr change per hour. Depending on the occupancy that may not be enough fresh air.

It may not be the case in your area but in most areas, if the walls are opened up (removing the t1-11) all the electrical,plumbing, and structural that is exposed "MUST" be raised to the current code, this can make a major difference in the cost of what you are considering and extend the payback for the added insulation beyond your and my life time.

[pelligrini]

Most likely you have R11 in the 70s 2x4 studding can only go to R13 max.

Probably right about the R11. It might have R13.

It wasn't available then but you can get over R23 with some of the closed cell products available today and used within the cavity of a 2x4 wall.

Art makes some good points, especially the code part.

[ironhat]

I'll respond in red to your queries below.

Most likely you have R11 in the 70s 2x4 studding can only go to R13 max.

unless there is another reason for removing the t1-11 siding . If it was me I would probabley consider putting a 1" or 1 1/2 faced high density foam board over the t1-11 leaving the t-11 there for structural purposes, as well as leaving the existing insulation alone, and then putting the siding over the foam board with glue and fasteners long enough to get into the t1-11. the Foam board will also generate an infiltration barrier which in a 70s house would gain you more then adding the insulation would. That was my original plan but Holmes on Homes had me convinced that you should open the walls to see what is going on, if anything, behind the siding. I didn't know what you said about code compliance and that changes everything. The only pressing potential problem would be behind the tub/ shower surround. I would also look at upgrading the windows if that isn't in you process already. We did that about 10 yrs ago with argon filled space. Much better. Your walls would end up being about as thick as 2x6 consturction with very similiar insulation values. Then, raising the attic insulation to 10 to 12" and insulating any crawl space would give you a very well insulated house. Both done. The reason behind all of this is that this is the SW facing, narrow end of a hip roofed rancher and contains the family room. I thought that the hip roof was an issue so I insulated the attic. That didn't make much difference in the summer or winter. Bear in mind that if the house is extreamly tight you may need to add mechanical ventilation in order to control moisture levels inside the house and provide sufficient clean air. The house now probably leaks 3 to 5 air changes per hour and what i've sugested above could bring it lower then 1/2 hr change per hour. Depending on the occupancy that may not be enough fresh air.

It may not be the case in your area but in most areas, if the walls are opened up (removing the t1-11) all the electrical,plumbing, and structural that is exposed "MUST" be raised to the current code, this can make a major difference in the cost of what you are considering and extend the payback for the added insulation beyond your and my life time.

I'm thinking that a reflective face on the foam board would not be a negative. If anything else comes to mind I'm wide open to suggestions. Thanks to all who have replied thus far. BTW, the overhang is 16" wide.

[Tamarack]

This Old House has had several episodes where they've used sprayed foam insulation.
It provides excellent insulation and superior sealing of air leakage, probably the highest R value out there. I lived in Fairbanks, Alaska for six years and the folks who used it up there couldn't praise it enough. It's used exclusively in Monolithic Dome Home construction, and the folks who are lucky enough to own one of those praise it highly also.
Unfortunately for me, there doesn't seem to be anyone within 200 miles of me that is equipped to do it. Once your siding is off it would be simple and fast to remove the existing insulation and replace it with this, and I'm sure you'd love the result.

Paul

[woodturner]

Can anyone comment or steer me to someone who can regarding the method, materials and feasability of such a project?

A couple of suggestions:

1. Read on the FHB site about siding, condensation, rotting, etc. Understand what causes those issues so you don't replicate them.

2. Wood framing is essentially a thermal "short circuit" in an insulated wall. There are some interesting studies looking at this issue - and how a 2x4 reduces the effective net insulation of the wall something like R-3. To minimize this issue, consider adding a layer perpendicular to the framing. One way to do this is to remove the siding, fill existing cavities with insulation, then nail 2x4's flat and perpendicular to the framing. Fill those (now horizontal) cavitied with insulation before siding. Now you have the thickness of a 2x6 wall but don't have the thermal short circuit.

3. Check out the insulation studies on the HUD site, and read Charles Wing's books to understand how insulation really works.

The dense-pack foams do work well, but are expensive. Dense packed blown in cellulose is a lot less expensive, and nearly as effective.

[woodturner]

Unfortunately for me, there doesn't seem to be anyone within 200 miles of me that is equipped to do it.

It's essentially the foam used in the foam sealer cans - great stuff, etc.

One can buy it as a two part product with an application gun, sold for contractors. Probably $200 for the setup.

I don't see why you couldn't do a whole house with that setup. Would take a little longer than the commercial wall-filling machines, but it seems like it would be a viable option, especially if you can't find a contractor to do it.

[BigguyZ]

There are online vendors who sell the equipment for DIY Foam spray. You want to make sure you have the closed-cell foam. The stuff in the cans is open-cell, which is far less effective.

[master53yoda]

[QUOTE=ironhat;463766]
"The reason behind all of this is that this is the SW facing, narrow end of a hip roofed rancher and contains the family room. I thought that the hip roof was an issue so I insulated the attic. That didn't make much difference in the summer or winter" This comment brings up a possible issue that is not resolvable with insulation.

Is the F room (family room) colder and warmer in relation to the rest of the house. If it is it may be a BTU per sq foot issue where the heat loss or gain in the F room is higher per sq ft then in the rest of the house and has insufficient heating and cooling being delivered to it in relation to the rest of the house. If the heating loss or gain is higher per sq ft in the F room then the room that has the thermostat then the thermostat is satisfied faster then the F room is and shuts off the heating or AC before the F room reaches temperature. It will cause the F room to have a greater temperature deviation from set point then the rest of the house.

This is why proper room by room load calculations must be done and the delivery system must be sealed properly or this happens. It is actually quite common in the residential environment due to a lower quality of workmanship and lack of system design.

[toolguy1000]

Most likely you will be told what you are allowed to do when you file for your building permit. your municipality probably has requirements for what is permitted within the context of residing your house. you were planning on applying for a permit, weren't you?