Sprayed-on cellulose vs. blown-in fiberglass??

16 years ago

This is a cross post with the HVAC forum.

We are presently evaluating different types of insulation for our home in Central Virginia. It is a Cape with several cathedral and 2 story rooms. We are trying to build as energy efficient of a home as possible, within our budget. We are using high efficiency heat pumps, energy star windows, brick veneer, metal roofing, ventless insulated crawl space, etc. We want to use a very good insulating material, but we do not want to use the sprayed-in foam. We are also not interested in using fiberglass batts. We were going to use the sprayed-on cellulose for the walls and the blown-in cellulose for the attic space; however, our GCs insulating contractor has recommended that we use the blown-in fiberglass system from Certainteed called Optima.

Besides the fact that these are obviously two entirely different products, I have not been able to find any good explanations of the side-by-side comparisons. I was told that the reasons for the Optima recommendation are 1) that they are concerned about using a "wet" product in our area of Virginia that has high humidity. Also, we have a large portion that is 2 X 6 construction and he is stating that it is difficult to determine if the product has fully cured; and 2)that the exterior membrane of the Optima product holds the fiberglass in place and even though there is settling there is less risk of damaging the insulation (or even losing pieces of the insulation) during the drywall installation vs. the sprayed-on celluose method.

In addition, he is recommending using fiberglass batting for the attic space vs. a blown-in product. He said that with the amount of ductwork in our attic area that we will receive more benefits from the batting than we would with a product that they would have problems installing correctly in all areas. Would it be unreasonable for us to request that he use a blown-in product and supplement it where needed with the fiberglass batting?

And, one other question. We wanted to use the low expansion foam around our windows/doors. He said that they would do it if we insisted, but that they would rather not b/c even the low expansion foams will lead to difficulties with proper window function. Has that been anyone else's experience? He wants to use fiberglass and caulk to seal these areas instead.

Thank you all so much! I know it is a long posting, and I do appreciate any feedback that you can provide!

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Comments (13)

worthy
16 years ago
low expansion foams will lead to difficulties with proper window function. Has that been anyone else's experience?

That is precisely the installation method I've used since the foam became available and it has never caused any problems I know of. I've lived in four of my homes myself. As well, it is also the method used by every high-end builder in our area. All I have to do is glance at the windows during the framing stage as I drive or bicycle by to see that.

On my last build, I even added some self-adhering flashing that is only used on commercial buildings.

For the attics, I use blown-in cellulose. It's cheaper than fiberglass and is not a known carcinogenic material (as fiberglass is). Blown material is ideal for an attic with all kinds of nooks and crannies and head-bumping trusses and roofs in the way. I can't imagine trying to cut batts to shape and carefully packing them in--unless maybe you're using blown-in insulation on top.
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sierraeast
16 years ago
We have blown in fiberglass by knauf in the walls that will not settle as it is a high density blown in product that is extemely packed giving a higher and truer r-value than standard batts. It makes sense what your contractor states about the moisture issue of cellulose as it is blown in damp, but not wet, and covering over with rock without it properly drying could cause some mold concerns, though i dont know that the dampness when blown in is that significant.Tough call as both are fine insulators.

I insulated around the gaps of our windows as the mfgr suggested not using foam. I asked the drywall hangers to leave a gap between the rock and the window jambs that i will fill with dap water based foam before i trim out the windows. The dap is an extremely almost non expanding foam that does not set up hard and stays flexible.It's not a good foam however for structural such as settin bath tubs, etc.

I agree with worthy that blown in in your attics is the best route as it fills all voids especially around ducting and protrusions.
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worthy
16 years ago
low expansion foams will lead to difficulties with proper window function. Has that been anyone else's experience?

That is precisely the installation method I've used since the foam became available and it has never caused any problems I know of. I've lived in four of my homes myself. As well, it is also the method used by every high-end builder in our area. All I have to do is glance at the windows during the framing stage as I drive or bicycle by to see that.

On my last build, I even added some self-adhering flashing that is only used on commercial buildings.

For the attics, I use blown-in cellulose. It's cheaper than fiberglass and is not a known carcinogenic material (as fiberglass is). Blown material is ideal for an attic with all kinds of nooks and crannies and head-bumping trusses and roofs in the way. I can't imagine trying to cut batts to shape and carefully packing them in--unless maybe you're using blown-in insulation on top.
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bungeeii
16 years ago
Ask your GC to contact an EPA certified inspector to consult with you about the best insulation methods. The way you're building will allow the GC to claim up to a $2K credit on his taxes if the house is EPA tested and certified. This consultation should only cost several hundred dollars. You'll not only have an objective professional advise you on insulation, but he'll also help you address air infiltration issues. (This might not be such a big issue if you don't have second story rooms with a lot of knee walls in your cape.)
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dixiedoodle
Original Author
16 years ago
Thank you all for your responses. Your replies are pretty much in line with my initial thoughts and impressions of the different products.

sierraeast-we are not in a huge hurry to drywall the house (within reason of course), so I am not that concerned about the moisture evaporating. Besides, we have not been moving at warp speed up to this point, and I see no reason to believe that my GC will suddenly have a process in place to change things. Anyway, I would imagine that for a product that recommends a 2-3 day evaporation period, an entire week + would suffice.

worthy- thank you for the info on the window insulation. Can you share a brand name of the foam? Also, I appreciate your thoughts on the use of blown-in cellulose in the attic spaces.

bungeii- I appreciate the advice on the EPA inspector. I don't know how far out they are scheduled, but we would like to be insulating on Monday. We already pushed them off this past week. I have a question about the air infiltration issues that you mentioned. We have 2 bedrooms, a loft area in our 2 story foyer, the bonus room over the garage, the office, and a bathroom all with knee walls. What exactly do I need to be concerned about in particular? From the way it was explained to me, the knee walls would be insulated in the same manor as the exterior walls of the house. Do they need to do something in addition to this? THANKS!
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bungeeii
16 years ago
The concern is that the knee walls would only have a face on the room side of the wall and nothing on the back side. But, since you're considering a blown-in product, there must be a back side.

But..... IF he's proposing the blown-in blanket, he might just plan on the netting going on the both sides of the knee walls, holding the insulation in as it's sprayed. Problem is, the area behind the knee walls is likely open to soffit, by way of baffles and/or space between trusses. The R value of that fiberglass insulation will be greatly reduced because of the amount of air that can/will pass over it.
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sierraeast
16 years ago
fwiw,if we'd had a choice, we would have went with damp blown in cellulose in the walls but no one in our area or even a raesonable distance installs it. I like the fact that it is non carcinogenic as worthy mentioned, and has borac inhibitors organic that help to thwart termites and other insects.The organic borac is also quite a fire retardant as well.The dampness as it blows in is miniscule and i would assume goes away faster than the 2-3 day recommendation even with high humidity levels in your area. A week plus would be more than enough timeframe i would think.
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cbtexas
16 years ago
We used the Optima and I really am glad my GC suggested it. I wanted to use foam but the cost was higher that balls on a giraffe for our area. The optima in combination with using solar board helps keep our house cool in the summer and warm in the winter. Here is a website that has great info as well as videos showing the product being installed.

CB

Here is a link that might be useful: Optima insulation
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dizzy8
16 years ago
Can someone please explain why low expansion foam would interfere with window function?
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niff
16 years ago
I believe the concern the GC is referencing is the issue of the (window) sill bowing out if too much expansion foam is applied around the window. However, most of the standard spray foam products found at the home centers (aka DOW's great stuff and that by DAP) are available in a low expansion formula specifically designed for window and door applications so bowing isn't nearly the issue as with the normal expansion foam products.

As worthy and sierraeast have suggested, the use of spray foam products around window and door voids is a perfectly reasonable -- some may say a best practice -- method. IN fact, many window manufacturers specifically call for foam spray in their installation instructions.

Personally, I think the spray is messy, and not cheap, but esp. in openings that are small and where you are try to insulate around shims, I think it is a very good product that lends good results.
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worthy
16 years ago
I have no brand preference--just low expansion or those that say designed specifically for windows and doors. The GC is 15 years behind the times.
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woodinvirginia
16 years ago
Contractors are "too cheap" to BUY the product especially made for windows & doors because it costs them more $$$ per install.

Thats why they are reluctant to utilize it. My contractor didn't even read Pella's directions when installing my windows; glad I was ONSITE to catch it.
The windows were installed wrong, I made him take them back out, READ the dang directions & install them per Pella's specifications.

Too often these guys think they knowitall or they have seen everything. Then the customer ends up holding zee bag.

That Optima product sounds like it is made for high humidity environments like Central Va too...I went to their website.
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ilmbg
16 years ago
woodinvirginia- will you please explain exactly what he did wrong installing the windows, so we other people who need to learn know what to watch out for?? Please?? Thanks
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Sprayed-on cellulose vs. blown-in fiberglass??

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Sprayed-on cellulose vs. blown-in fiberglass??

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