Improving insulation on old house
sandle64
| Posted in Energy, Heating & Insulation on
Greetings. This is my first time here.
We are planning to renovate/add onto our house, built before the first oil crunch. We will be resheathing and residing the house, so the 2x4s and any old insulation (??) will be exposed. How do I improve the energy efficiency? Use high R value foam (still only 20-25 R for the width of the 2×4? Nail 2x2s perpendicular to the studs to give me more depth? Tear it down and start again with 2x6s?
Thanks
Replies
Sandle- Welcome to Breaktime.
You have a profile that can be seen by others. If you click on your name it will open up and you can fill us in where you are located. This will mean a lot when discussing insulation.
Cheers
'Nemo me impune lacesset'
No one will provoke me with impunity
Here in the Northeast, anytime you have an exposed wall and can get a vapor barrier in, do it. (unfaced, then vapor barrier, then sheetrock or plaster.)
I renovated my old farmhouse and blew in fiberglass through the siding in areas and although it made a big difference, comfort was almost entirely due to sealing air gaps and the new windows and doors. As I'm doing one room at a time, you can notice a dramatic difference in the rooms where we gutted to studs and adding fiberglass and vapor barrier vs. blow-in and trying to seal all those holes.
R20-21 is pretty darned good for 2x4 wall. Are you talking about the spray expandable foam? That stuff is really great because not only does it give you a higher R value per thickness, but it also hardens and gives the building itself more structure, more ridgidity. If you did that, then covered the sheathing with half inch siding foam board and taped all the seams (very important), then tightened up all windows and doors, you should be in fine shape.
Post where you live.
I have been contemplating the same thing.
While foam looks appealing, it is very energy intensive to manufacture and it is quite toxic. That said, it has its place.
I am considering blown in cellulose for my application. It is fireproof and recycled. The r-values per inch is close to foam- depending on the type. It is also quite a bit cheaper than the foam.
I have been in homes that have the cellulose insulation, and the comfort level is much better than fiberglass. I have not experienced a foamed house.
I will probably use foam panels on the exterior.
We live in the lower Hudson River valley, about 30 miles north of New York City. The house is exposed to wind (sometimes severe like two nights ago) and the portion to be renovated is the north end, hence the desire to improve the insulation. And yes, the R-20+ value for the 2x4 thickness was based on using expandable foam. Ideally we would like the cost to be reasonable, so the equation may come down to additional thickness plus blown in cellulose versus current thickness plus foam. Either way, anyone familiar with the local utility prices here will figure that the return on investment will be fairly rapid. Thanks for all the input.
Hi,"While foam looks appealing, it is very energy intensive to manufacture and it is quite toxic."I am wondering where the "quite toxic" comes from -- I was under the impression that the new foams are fine?Thanks,Gary
The cured foams themselves are NOT toxic. They burn to release toxic fumes, but if your house is on fire you have bigger problems to worry about if you don't get out by the time flame breaks through the drywall. Carbon monoxide released by the partial combustion of ANY building material is more than toxic enough to kill you.
One of the two reactive compounds used to make the blown foams IS toxic. Both icynene-type open-cell foams and "hard" (closed cell" polyurethane foams use isocyanates to react with a lower-toxicity or non-toxic 2nd chemical to make the foam. Isocyanates are both extremely toxic AND extremely short-lived in the environment since they react irreversibly with water vapour. The toxicity of isocyanate-bearing materials are a definite concern for the people who apply these foams, but within about 24 hours after spraying there is no more isocyanate to worry about. Breakdown of the foam over time, should it occur, will NOT regenerate isocyanate, so there is zero risk of isocyanate off-gassing over time. The chemistry that makes the foam is not "reversible". Tests have verified that foams like Icynene do not represent a hazard by releasing VOCs. Indeed these foams are even used in homes designed for people with so-called "20th century disease" or acute environmental sensitivity.
Polystyrene foam is a different animal. Polystyrene is made from styrene, and does continue to out-gas some minute quantities of styrene basically forever- you can smell it when you break a piece of EPS board etc. Styrene is toxic, though only mildly toxic by the standards of many industrial chemicals. If you're worried about styrene, or formaldehyde, or phthalates, or vinyl chloride, or any other volatiles released by modern plastics, then there are numerous articles in your home to be concerned about to a greater degree than a layer of EPS or XPS foam insulating your home, hidden behind a layer of vapour barrier and taped drywall. If you ARE concerned about these compounds, you should stay away from cars completely- that "new car" smell is an utter soup of those compounds.
As to the energy argument: cellulose is a recycled product and has a lower "embodied energy" than a sprayed foam product, and can work well as an air barrier too- it's definitely the "greenest" insulation material available. But ANY of these insulations, foams included, will save more energy and reduce environmental impact to a degree enormously greater than the energy and environmental impact resulting from their manufacture. You should be far more worried about ensuring that the insulation and building envelope are properly installed to do their job than you should be about the energy used to make the insulating materials in the first place.
In terms of bang for the buck, the best thing you can do when the sheathing is off is to airseal the structure. This is actually easier from the outside than the inside.
Seal around the bottom and top of the drywall (floor joints are usually the worst), the sillplates, and the rim joists. Use foam or caulk, depending upon the gap in question.
Seal around electrical outlets, including where the wires enter the box, and all the little holes in the back of any typical box.
Seal any other mechanicals protrusions. Pipes in exterior walls deserve a sealed foamboard chase.
Add fireblocking as missing, and airseal that.
After that, densepack cellulose has the best cost/benefit ratio.
search for PERSIST
My memory says that it was developed in canada so its good for colder climates. I believe it involved no wall insulation but had foamboard on the sheathing and extensive air sealing. the devil is in the details.
eric
If you scroll down in the lower left corner of your screen there is a search function that will take you to previous threads dealing with whatever you type in the search bar.
If you type in 'PERSIST' you'll get a supply of data from those old threads.
Cheers
'Nemo me impune lacesset'No one will provoke me with impunity
Time vs Money...
Spray foam
Polyurethane based hard foam highest r-value per inch and perm rating less than .05. Acts as its own Vapor barrier. Highest cost, fast install by pro's
Soft foam, different brands, High R value, seals out air very well, Second highest cost, fast install by pro's
Cellulose
Wet spray, Moderate/high R, seals well vapor barrier still necessary where required. Re-cycled product, non-toxic. Lower installed cost, fast install by pros.
Dense Pack Dry, Moderate R, seals well, dusty and labor intensive but you can do it yourself with good results. Low material cost, installation takes time, yours or the pro's. cost varies with time.
Ridged Foam
Rip foam to fit joist cavities less 3/8 - 1/2" use expanding foam (find a gun to dispense high volume cans) to seal to framing. Two layers of 1 1/2" and 2" fill the standard 2x4 stud bay. High R value, seals out air very well. High material cost, labor by you -priceless, sorry, labor cost low. Slower than other methods.
In some areas 1/2" or 5/8" ridged foam is installed outside the studs, extra R value, eliminates thermal bridging, requires window and door trim-extensions.
Be sure to have enough shear strength if you do not use wood sheathing.
Fiberglass
Least expensive, my last choice, does not block air. Needs vapor barrier to keep out moisture, hard to do with an exterior instillation. low cost.
The BIG question is how long you plan to live in the house. The longer you stay and the higher heating and cooling cost go the better the high R value/tight sealing options will be.
As mentioned in an earlier post sealing up all framing joints with foam and/or caulking will make a big difference.
Good luck and keep warm,
Garett