School me on home insulation

[sbornia]

Next big home project will be new insulation, which I knew nothing about until 10 days ago. Now I know a little, so I turn to your collective wisdom for more of a clue.

House is small (1200 sf) and old (1916). Attic has 30 year-old cellulose that’s lived its full life. Two contractors recommended replacing it with new cellulose, treated with borate, one at R-38 the other at R-50. $600 price difference. Third guy recommended a different material entirely, mineral wool, but haven’t seen his estimate yet. All recommend air sealing the attic.

The floors have zero insulation now. Pricing and points of view are all over the place. One guy swears by Ultratouch Denim, the other formaldehyde-free Knauf Ecobatt fiberglass. Denim advocate says denim works better in real-world situations, and that rodents like fiberglass. Fiberglass advocate says that denim is vulnerable to moisture, difficult to work with, and product quality can be iffy. Both recommend R-19 for their material of choice. Denim is 50% more expensive than fiberglass.

Everyone recommends doing the walls as well, but that will add about 50% more to the total project cost and be majorly disruptive, so I don’t see us going there, as effective as it might be.

Any experience and tips you can share would be appreciated. This may end up being 2X as expensive as the (wishful thinking) number I had in my head, so I want to do it right.

Thanks!

[NYCfixie]

Next big home project will be new insulation, which I knew nothing about until 10 days ago. Now I know a little, so I turn to your collective wisdom for more of a clue.

House is small (1200 sf) and old (1916). Attic has 30 year-old cellulose that’s lived its full life. Two contractors recommended replacing it with new cellulose, treated with borate, one at R-38 the other at R-50. $600 price difference. Third guy recommended a different material entirely, mineral wool, but haven’t seen his estimate yet. All recommend air sealing the attic.

The floors have zero insulation now. Pricing and points of view are all over the place. One guy swears by Ultratouch Denim, the other formaldehyde-free Knauf Ecobatt fiberglass. Denim advocate says denim works better in real-world situations, and that rodents like fiberglass. Fiberglass advocate says that denim is vulnerable to moisture, difficult to work with, and product quality can be iffy. Both recommend R-19 for their material of choice. Denim is 50% more expensive than fiberglass.

Everyone recommends doing the walls as well, but that will add about 50% more to the total project cost and be majorly disruptive, so I don’t see us going there, as effective as it might be.

Any experience and tips you can share would be appreciated. This may end up being 2X as expensive as the (wishful thinking) number I had in my head, so I want to do it right.

Thanks!

We had two architects (friends) and two builders (friends) look at our 1940s NJ 1800sqft house with plaster walls but no insulation in them and only fiberglass insulation in the attic (not original to the house) for energy/heating/cooling.

- All said replacing windows and sealing doors would have the most impact but it is the most expensive. We replaced all windows over about 3 years and it made a huge difference.
- They also said it was more important to seal the "bottom of the attic - ceiling of the top floor of the house" because once the heat/cool was in the attic you lost it for good. Attics need to breath so the new thinking is that you do not insulate under the roof unless you finish the attic and it becomes living space.
- All recommended spray foam for our unfinished attic but that would mean taking up the floor in the attic - which was an old attic floor, very time consuming, and costly (not more than windows but not cheap either).
- We used denim in the few walls in the area when we gut renovated back to back upstairs bathrooms (master, hallway) near the bedrooms. Moisture barriers were installed. Our contractor refused to use fiberglass in the walls because it is not healthy and he said cellulose in walls compacts and thus does not work in these situations. Foam was cost prohibitive for such a small space.

What we learned...
- More heat is lost via windows and doors then via the attic (in most situations)
- What insulation one uses depends on the situation

[NYCfixie]

...

Everyone recommends doing the walls as well, but that will add about 50% more to the total project cost and be majorly disruptive, so I don’t see us going there, as effective as it might be.

...

Forgot to add...

We were told doing interior walls only helps with sound so there is usually not a point to it especially in older homes that have much thicker walls. Exterior walls would save the least energy loss and only made sense after replacing windows and sealing the attic floor.

[Bob Ross]

Our contractor refused to use fiberglass in the walls because it is not healthy and he said cellulose in walls compacts and thus does not work in these situations. Foam was cost prohibitive for such a small space.

I'd be curious what their impression of rigid fiberglass -- e.g., Owens Corning 703 or 705 -- are, since they don't compact, are as easy to install as foam (expanded polystyrene) sheets, and arguably have none or at least few of the health issues that plague loose fiberglass.

[rwsaunders]

See page 110 of the latest (2017 Title 24) CA energy code for insulation requirements for existing residential construction. You might want to ask your contractors to certify that they are installing insulation to ratings which will be code compliant and make sure that they are licensed in CA...you can look that up on a state website. Here’s a quick guideline from Johns Manville and I linked the code as well. On a related note, fiberglass is an acceptable material for insulation as are other materials and it is the most commonly used material in the industry.

https://www.jm.com/content/dam/jm/gl...le24_Flyer.pdf

https://www.energy.ca.gov/2015public...15-037-CMF.pdf

Contractors State License Board

[steamer]

Keep in mind that there is very little difference in the heat transfer through R-38 vs. R-50. Heat transfer is proportional to the inverse of the R value.

I wouldn't bother with the R-50.

Also, I have the denim stuff in one exposed floor area at my house. Had it about 10 years. No long term issues. I chose it over fiberglass because it was easy to work with and I liked the idea of using a material with a very high recycled content. But fiberglass is fine too. Rock wool is a little better if you can get it, and are willing to pay a llittle more for it.

[sine]

Any sign of critters in the attic.....turds, nuts, etc.?

If yes, seal all entry points. It's hard messy work as you need to reach all the small spaces. In our house in Maryland I used a combination of steel wool and foam insulation.

Next, if you have any, clean out moldy insulation. Wear a very good mask. Then I would purchase bags of cellulose insulation and spread it around the attic "floor" myself. Lots of crawling around carefully if you have tights spots.

Not sure what contractors mean by air sealing the attic. As posted earlier, attics need to breath....soffit and ridge vents are a must. Both our homes in Maryland (built in 50's and late 60's) did not have soffit or ridge vents and it showed. We added vents to the 60's built house and the improvement was dramatic.

With the money saved with the attic diy, tackle doors and windows. You might be able to improve door seals yourself.

Walls. Spray foam for exterior walls is best as it will get into little spaces and stay there. House would need an exterior wrap. Major project to do it right.

On Habitat houses I worked on we used Denim on some interior walls for sound proofing.

[sbornia]

Thanks all, good stuff. Windows are already all double-pane, and door seals all check out. New furnace and central heating system installed in 2016. We had an energy audit done last year and the only recommendations were for insulation. The three contractors I'm getting estimates from are all licensed and insured in CA, and their customers seem to like them. They're all approved by the city's and state's energy conservation programs, too, fwiw.

No critters in attic or crawlspace. Attic has good vents. The air sealing these guys mean is around cracks, holes for wiring, recessed lighting. Hard for me to tell how much actual work this is, but their estimates were close.

The guy who recommended R-50 cellulose over R-38 in the attic did so "to account for settling, deterioration, climate change and rising energy costs. Most of the cost associated with installing this insulation is prep time and labor. Once we are all set up, the extra labor involved with installing to R50 is negligible, and the material cost difference is minor. Also keep in mind that one cannot achieve even R38 levels where it pinches down at the your roof's eaves. So a higher amount in the center helps make up for this.” Sounds plausible? I don't think his higher price over the other guy is solely due to the extra material, I suspect he's just a bit more costly for some parts of the project.

As for DIY, if only I had the time and skills. This is one project we'll pay pros to do it.

[steamer]

The guy who recommended R-50 cellulose over R-38 in the attic did so "to account for settling, deterioration, climate change and rising energy costs. Most of the cost associated with installing this insulation is prep time and labor. Once we are all set up, the extra labor involved with installing to R50 is negligible, and the material cost difference is minor. Also keep in mind that one cannot achieve even R38 levels where it pinches down at the your roof's eaves. So a higher amount in the center helps make up for this.” Sounds plausible? I don't think his higher price over the other guy is solely due to the extra material, I suspect he's just a bit more costly for some parts of the project.

Yeah, that sounds pretty plausible. I just didn't want you thinking that R-50 was 31% better than R-38.

[thollandpe]

Steven, I've done a ton of this work on older homes. The best places for you to spend your money are in the attic and basement, so it seems you're on the right track.

Attic: heck yeah, bury it in cellulose. Air seal first. By far the most cost-effective thing you can do is fill gaps with foam, block up big openings with rigid foam sealed around the edges with spray foam, and fill with cellulose. Think about the details of where you need access later, like a catwalk, and what will happen to that deep pile of cellulose near anything like a gable vent or windows. Borate-treated cellulose is a great fit here, you don't need the moisture resistance or physical strength of mineral wool in the attic.

Consider a sealed-and-insulated attic hatch like the Battic Door (Battic Door(R) Home Energy Conservation Insulation Products). PM if you need one.

Why are you insulating the whole subfloor, is it over a dirt crawl space? The #1 best thing you can do down low is seal the perimeter (rim band) with 2-part spray foam. They should wrap it up against the subfloor and down onto the foundation. This is the single most effective air sealing and insulation measure you can do. I'd stay away from both denim (cotton) and fiberglass for the subfloor. Rodents do love fiberglass, it's a nightmare in a crawl space. I've used 2" Thermax (foil-faced polyisocyanurate) sealed at the edges with single-component spray foam for this. You could also consider netting with dense-packed cellulose, but that could make accessing any wiring devices or piping you have in the joist spaces a pain in the ass.

If you do use a moisture-permeable insulation like cellulose, denim, or fiberglass over a dirt crawl space, be sure you seal off the dirt with scrim-reinforced poly. Either buy the world's best tape (Siga) to adhere it to the concrete walls. Or bring it right up the walls and staple it to the band joist, and then foam over that.

[thollandpe]

Regarding R-50 vs R-38, once you've paid to have the truck parked in your driveway and a person up in the attic with the hose, you may as well have them pump in a few more inches. That extra R-value will never be cheaper, and cellulose is cheaper than dirt. No really, go to Home Depot and get a bag of cellulose. Then push your cart to the other side of the store and get a bag of potting soil. Cheaper than dirt. (Stole that from John Straube, University of Waterloo energy guru)

Bruce Harley's book on Insulation and Air Sealing is a great resource: https://www.amazon.com/Insulate-Weat.../dp/1561585548

Cheers, Todd.

[sine]

edit

Consider a sealed-and-insulated attic hatch like the Battic Door (Battic Door(R) Home Energy Conservation Insulation Products). PM if you need one.

Some interesting products. Thanks for sharing.

[sbornia]

Steven, I've done a ton of this work on older homes...

Thank you SO much.

[nahtnoj]

I'm going through this now. Stone house built in about 1850 with an addition that is about the age of your home. The stone part is stone - the walls are 24" of field stone. The addition is wood framing.

I could write a short novel about what I've done in the past month to address a range of deficiences, but I will focus on one specific thing that I don't see anyone talking about: a vapor barrier.

Air sealing isn't the same as a vapor barrier.

You want to do something to keep moisture from your living area from rising into the attic. Its difficult as a retrofit, but necessary. Special paint might be your best option.

This should be addressed before the cellulose goes in.

[sbornia]

I will focus on one specific thing that I don't see anyone talking about: a vapor barrier.

Good point. One of my prospective contractors recommended installing a vapor barrier on our crawlspace's dirt floor and sealing the crawlspace vents, but the other recommended against it because some parts of the crawlspace are not accessible enough to install the membrane. He had an "all or nothing" point of view on the matter. Hard for me to know who's right.

[j44ke]

This Old House is doing a net-zero renovation, and I remember at least one episode has to do with sealing underneath the house. I just mention it because the episode seemed to give a good overview of the goals and some of the techniques mentioned above, not necessarily because they are the experts in this area or anything.

[steamer]

Good point. One of my prospective contractors recommended installing a vapor barrier on our crawlspace's dirt floor and sealing the crawlspace vents, but the other recommended against it because some parts of the crawlspace are not accessible enough to install the membrane. He had an "all or nothing" point of view on the matter. Hard for me to know who's right.

It doesn't have to be all or nothing. A vapor barrier over the portions that can be accessed will still reduce moisture migration. Good crawlspace ventilation can help too by making the crawlspace dewpoint nearly the same as the outside air. You don't really want to go sealing up a crawlspace. It would probably violate the building code anyway.

Also, be aware that a lack of a vapor barrier on the dirt in a crawlspace can certainly allow additional moisture to get inside by way of diffusion. But be aware that air leakage is a much more powerful effect. Diffusion of water vapor is much less of a concern than air leakage of moisture laden air into the building. The former brings in a few teaspoons while the latter can bring in gallons (so to speak).

So, as has been posted above, focus on insulation and stopping leakage. Vapor barriers have their place, but in a climate where you live, they aren't necessarily the thing to focus on.

[thollandpe]

Vapor barrier gets a bit more complex, and will certainly depend on your local climate conditions. It will also depend on what you want to do with the house. In New England, one common vapor barrier and insulation system that works AOK for heating can be a disaster if you cool the house.

Steven, it looks like the contractor who wants to put poly in the crawl space is on the right track.

TH

[nahtnoj]

Good point. One of my prospective contractors recommended installing a vapor barrier on our crawlspace's dirt floor and sealing the crawlspace vents, but the other recommended against it because some parts of the crawlspace are not accessible enough to install the membrane. He had an "all or nothing" point of view on the matter. Hard for me to know who's right.

I meant a vapor barrier for the attic.

Our second floor ceiling is actually tongue and groove wood. We therefore have no effective way to prevent moisture (and heat) from the living space from rising into the attic, which has major humidity problems. We also have an AC system living in the attic. So we're going to spray 6" of closed cell onto the sheathing and bring the attic into the conditioned envelope of the house, and remove the blown in insulation from the attic floor.

But you're in quite a different climate zone than me, so take some of this with a grain of salt.

Our basement is mostly dirt floor. That's going to be a big project.

[chris7ed]

I considered spray foam too. It has, like everything, a number of drawbacks. Decided not to use it. Haven't decided what to use.