to insulate or not to insulate

shakushinnenApril 19, 2012


I have a question, which will require a guesstimate from someone who knows the impact of insulating, specifically in the roof, above the ceiling.

We live in Markham, just north of Toronto, and are considering blowing insulation into the roof area of our 1700 square foot brick bungalow. We have done all the other walls in the house, and are considering doing this, when the kitchen is being renovated. However, it's going to cost us and additional $1,700 for this job, and we're not really sure if it will be economically feasible. This is an old house (double bricked) built in the late 60's when heating costs were not a majour concern. The contractor says that it is currently about R10, and that inslulating it would increase it to R50. Is there anyone out there who can give me some sort of guesstimate as to how much we might save on our heating bill (%wise), assuming cold winters. We will likely be in the house for the next 20 years, assuming we live that long.

Thanks for your help. I know this is a tricky question, but I'm really not sure if we should spend the money or not.

...... john

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heat loss from unisulated attics is about 30%
if you air seal between living space and attic before
adding insulation you will see a savings, and an
improvement in comfort both summer and winter.

best of luck

    Bookmark   April 19, 2012 at 2:13PM
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Hi energy_rater_la,
So, you're saying that there should be an air seal between the insulation and the ceiling?
..... john

    Bookmark   April 19, 2012 at 6:47PM
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Energy_rater means that you have to make sure all the holes are closed. Examples of holes are "can lights", holes drilled for cables and poorly sealed HVAC boots (if you have them in the ceiling).

    Bookmark   April 19, 2012 at 7:55PM
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You could buy the insulation for about $850 and that would come with a free rental. It is certainly less than a day job.

I'd venture to say that you would save 25% of your heating costs.

    Bookmark   April 19, 2012 at 9:48PM
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Hi Ionized,
I'm sorry. I haven't the slightest idea what "can lights" or "HVAC boots", or even "holes drilled for cables" are.
Thanks David,
If I do do it, I will probably get the contractor to do it. I'm not a home improvement kind of guy.
However, 30%, 25%, even 15%, would probably be enough of a saving to justify doing it.
.... john

    Bookmark   April 19, 2012 at 10:33PM
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can lights are recessed lights
if Insulation Contact IC they have holes
in the housing. you will be able to see light
thru the holes when in the attic.
retrofit by boxing in with ice chest with 4" clearance
on top and sides, cutting ice chest to fit tightly to
attic floor and caulking in place.
or buy air tight inserts to retrofit from inside the

hvac boots are the supply box that attaches to attic floor
and supply grill on inside of house. I use mastic tape
remove the supply grill from inside the house and
seal sheetrock to inside of supply box (hvac boot)

at the same time mastic seal plenums (supply and return)
to equipment, and mastic seal ducts where they take off
from supply plenum. I use hardcast brand mastic tape
and paint on mastic that is applied with a brush.

electrical & plumbing penetrations are also sealed
prior to insulation install.

if you insulate without doing any of this you will
still see a savings, but to do these things before
insulating you will improve the indoor air quality
of the house (esp if using cellulose)

the average house has 30% duct/return leakage.
in our hot humid climate these leakage areas
introduct humidity laden air into the house.
hvac has to work harder to remove humidity.

while I understand the frustration of adding to
the list when wanting to simply blow insulation
and be done with it..these areas make a huge difference
in how the house performs.

insulation is essentially useless when air moves
through it. to complete the air barrier, and
minimize duct/return leakage is the right thing to do.

also be aware that cellulose creates a fine 'dust'
(actually borate treated newspaper) that enters
through small cracks in attic floor into house.

we can help advise your diy if you'd like.

best of luck.

    Bookmark   April 20, 2012 at 12:11PM
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Thanks again,
My contractor didn't mention anything like the things you speak of. I think he just intends to blow insulation into the space between the ceiling and roof. You, of course, would not recommend this. I would imagine that doing it 'the right way' will add significantly to the cost, probably rendering not cost effective (from my point of view). So, the question is, what would be the heat savings if he just blows the insulation in, without any of the steps you recommend? Any thoughts? Would you recommend this over doing nothing.
..... john

    Bookmark   April 20, 2012 at 7:23PM
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The frustrating thing is that a basic air sealing should be a few hundred dollars and perhaps increase savings from 25% to 35%. Caulk is pretty cheap. Even with the labor we aren't talking much.

In the end $1700 is not a terrible price for the insulation so you might ask him about air sealing - it won't be that bad.

With an old house, you might not have that many penetrations. Recessed cans were not that popular and I would presume you don't have forced air heat with ducts in the attic. Those are the 2 biggest leak points. Next is probably bathroom fans. After that, overhead lights and smoke detectors. All of these things are less common and less numerous on older houses. In a newer house, these things add up to tremendous leakage if not properly addressed.

    Bookmark   April 20, 2012 at 8:35PM
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or you might diy some of it yourself.
better to seal before insulating.

most insulators just blow and go.
if they told you a 30% savings and you
only get 10%..oh well.

it is up to the homeowner to get the details.

best of luck.

    Bookmark   April 21, 2012 at 12:45PM
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Hi guys,
I've asked my contractor if he feels that sealing will improve the effectiveness of the insulation, and ...... if his quote includes the sealing. I'll let you know what he says.
Thanks. I appreciate your guidance,
..... john

    Bookmark   April 22, 2012 at 6:23PM
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"With an old house, you might not have that many penetrations."

You should see all the holes between the attic and living space in my 1930s house :-(

OP, don't forget a plan to seal up the access point to the attic, scuttle hole or stairs.

    Bookmark   April 23, 2012 at 11:26AM
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and if your heating system is in the attic
you'll need 30" service platform and
a clear walkway to access it.
walkway also to water heater if applicable.

best of luck.

    Bookmark   April 23, 2012 at 5:04PM
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Hi again,
Our contractor said that to put an air seal in our house he would have do majour renovations on the space about the ceiling, and that he intends only to blow insulation into that space. I reiterated my concern wrt whether the job is worth doing ...... $wise. After speaking with his insulation contractor, he told me that I can expect to save between $300 and $500/per year on my heating bill, and feels this is a conservative estimate. This would be between 17% and 28%, and seems to agree with what's being said here.
....... john

    Bookmark   April 23, 2012 at 7:29PM
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If you turn every light on in the house and go in the attic armed with a caulking gun and flashlight and seal anything that you see light coming through or where any wire or pipe you can find that goes from the attic down into the living space even just a few adds up. After you find some you will get 'snoopy' and want to find more. Each recessed light in my house was leaking 5cfm (cubic feet per minute) and I have 14. This is not including where other pipes and wires enter and exit.

If you seal only 20 cubic feet per minute of air leaks which doesn't seem like much but in a day thats 28,000 cubic feet in a DAY. A living space 50x50x8 has 20,000 cubic feet of air. If you THEN add insulation on top of that and do some other sealing here and there and some duct sealing the difference in comfort and money savings really will become noticeable.

If someone is going to seal its a WHOLE lot easier now than after a load of insulation is on top of everything.

The old 'cellulose' will pack in and seal the cracks and gaps is garbage. It will help somewhat but nothing like sealing the leaks shut and air going through cellulose or fiberglass as you open and close doors will pull dust and other stuff out of your attic in.

    Bookmark   April 23, 2012 at 10:31PM
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Thanks for the advice.
I'll have a look.
..... john

    Bookmark   April 24, 2012 at 1:59PM
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