Older homes and insulation

[JacquieJet]

Hello all,
A quick question for those of you that have finished a third floor loft (attic) in your homes...
We have ours "finished" by a PO, there is flooring and walls but zero insulation. It is VERY cold in the winter and very hot in the summer, and the heat loss through our roof is huge. Anyway, as we have another baby on the way, we are going to be converting it into our bedroom to make room on the second floor for the baby.
Obviously, we are going to need to tear down the walls, etc, and insulate- otherwise we will turn into popsicles in the winter! I was thinking of doing a closed cell spray foam, as we just did our garage that we built last year and it turned our brilliantly. But, I worry about sealing up an old house too much (spray foam also acts as a vapour barrier).
So... does it matter how we insulate? We aren't doing anything to insulate the first two floors, as they are still the original lathe and plaster and there is no reason to disturb it, so will our house still be able to "breathe"? Or will spray foaming the loft lead to an issue down the road anyway? Mould, etc?
Any guidance/experience would be appreciated! Thanks!

[GibsonGM]

Hi JJ....I suppose you COULD do it w/spray foam that way, but how would the lower floor bays in the wall breathe? I had the same dilemma in my farmhouse. Post and beam, so open wall cavities, but I wanted to finish off the 2nd floor.

We had dense pack cellulose blown in, the entire house. R-20 walls, R-60+ attic. It goes in under (low, 4psi) pressure, and doesn't harm plaster. Not much disturbance...you could get away with a few holes outside, a couple under windows. You may NOT have to demo the top floor if you do this, they may be able to blow in behind the walls as is!

Dense pack is ideal for homes w/no vapor barrier. It is hyrdophobic, so doesn't "like" water...it wicks it and distributes it to dry, if any gets in. It rejects interior moisture due to the pressure it is inserted at. It does not mold. It's 1,000,000x ahead of any fiberglass thing...won't rot your walls, in other words. It closes those fire-channeling bays, too! It would only smolder, not burn, if there were a fire. +10,000 in my book.

We have been totally impressed here so far - my 2nd floor stays 70F with a small fire in the wood stove on the 1st floor. 25F nights right now.

I'm more partial to dense pack because it COULD be sucked out if there a bulk water problem, doesn't permanently affect the home, isn't affected much by shrinkage of wood framing, repels rodents, etc....I suggest you consult with someone who installs it - find a pro thru you local hardware store. Oh, <$3,000 for our cape & ell!!!

I also had thought to leave the 1st floor open, but that is BAD NEWS...moisture will condense on the lower part of any insulation (foam...) you put above those bays. It'll drop down onto the sill over and over until it rots Kind of all or nothing, to be safe. The dynamic of the house changes if moist air can't get out the attic as it has been, and that needs to be considered and known so you can deal with it.
My case, it's a bathroom fan, kitchen range fan, and plastic in the dug crawlspace, your will vary.
My humidity now is between 30-50%, so all is good.

Hope this helps...

[JacquieJet]

Super helpful! Thank you so much, Gibson! That actually makes a lot of sense, and sounds like it would be a good solution to our issue. Demo-ing the loft isn't a huge issue as the ceiling is a drop-type panelling and the walls are painted 1970's vertical wood panelling... no huge loss there, haha. But, I like the attributes to the dense pack you mention, specifically the reduced flammability and also how it deals with moisture.
Thanks for sharing! I will absolutely look into this.

[Mick_VT]

I believe that there are baffles that can be installed to provide a cold roof / airflow when spray foaming underside of roofs

[vvzz]

Hello all,
So... does it matter how we insulate? We aren't doing anything to insulate the first two floors, as they are still the original lathe and plaster and there is no reason to disturb it, so will our house still be able to "breathe"? Or will spray foaming the loft lead to an issue down the road anyway? Mould, etc?
Any guidance/experience would be appreciated! Thanks!

Before proceeding, I recommend familiarizing yourself with the latest knowledge in building science. It's a complex topic and there are a lot of concepts like 'breathing' that are often used incorrectly. Take a look at this book: https://www.amazon.com/Builders-Guide-C ... =lstiburek or other books by the same author(Joseph Lstiburek)

[GibsonGM]

YW, JJ, I enjoy this stuff.

Yes to both replies above....baffles CAN be done, IF you do spray foam (which I oppose...if you ever develop a leak in your roof, you will have rot before you know about the water infiltration. Plus, it is forever). There is nothing wrong with a hot roof, but you DO need to know 'some stuff''. If you have a metal roof, or slate, that is idea. Asphalt roofs prefer the airflow underneath. Baffles require you to have a ridge vent, we don't know if you have one at this time (pic?). Often, gable venting is easier in an old, previously un-vented home...that is what I chose.

You can visit buildingscience.com, lstiburek's site, for TONS of info on this. Ideally, you would build in your room, and leave some space at top for a vented attic area, if possible. Then you would dense pack up to this area, and loose fill the top (attic floor). The gable vents deal with any moisture, and this constitutes a 'hot roof' situation. Again, site-specific.

Can you provide a pic of your house, showing the 3rd floor (a window or something)? Just curious. A GOOD reputable dense-pack installer will know what's right for you. Yet another dense pack benefit....with no vapor barrier in the house, it allows for some back and forth with moisture, with no mold. It takes it in, gives it back. Spray foam, to my understanding, allows actual condensation on its surface, behind the wallboard material. Done right, the risks of this are not great with either tech, I am just biased to dense pack cell. Your house should never get damp enough inside for this stuff to happen, being conscientious as we all are

You HAVE to do the whole thing right, as a good contractor suggests, or you will negate any benefits. No matter which method you go for...can't stress that enough!

[Gothichome]

JJet, read this
https://buildingscience.com/documents/b ... kages/view
The building science group is a wonderful site with all sorts of really well thought out techniques. Also, one of the major contributors is a Canadian, so he must know some thing about keeping warm in February. Lots of info for us old home folks (not to be confused with us OLD home folks).

[JacquieJet]

Thanks vvzz and Gothic for the links! Very helpful!

Here are some pics... The exterior of the house, and the loft, looking one way and then the other way. Please ignore the mess!!
Oh, and since it was mentioned, yes we do have a steel roof. Thanks!

Edit: Sorry, I just realized the pictures were sideways! :/

[GibsonGM]

Hi JJ,

I also suggested building science, lol There is a TON of info on that site. It's where I (and most others probably) started to learn about dew point location in or out of your wall, ha ha. Is that a brick home, or is the stucco just decorative?

Whatever you do, you will likely not want to leave the wall cavities BELOW where you insulate hollow. You will want to ensure that you have a vapor barrier in the basement, whether concrete or a plastic membrane, depending on what's there now.


Your 3rd floor is the same as my 2nd, as mine is a smaller Cape. You can dense pack the knee wall, the angle, and loose fill the top, if you vent the gable ends. Can't see what venting may be there now in the pics. Probably little modification to the walls if you do it that way, provided they are hollow, deep enough, and can be accessed from above (that's what I did, plus just few 2" holes in the sheetrock to patch). I have 6" of d.p. in my walls/angles, and 18" on top....

The first thing you do is consult with a reputable insulation installer, whose name you get from your local stockyard of good repute. We here have probably done this by fiberglass, blow in loose cell, blow in fiberglass, Roxsul, spray foam, and dense pack, and all have different opinions! Technologies have changed a lot since the 70s.

Spray foam scares me in older homes because you cannot see what's happening behind it, and it is not removable to fix any water issues which may arise unexpectedly. Plus, it's quite expensive compared to dense pack.

YMMV. (your measurement may vary)

[Kmarissa]

This is such an interesting question. We have a very similar arrangement with an attic space finished by a previous owner, except ours tends to be far too hot in the summer as well as in the winter (in the winter, we can just close the heating vents and the space becomes comfortable, but in the summer we need two window AC units in addition to the central air, and the window units still struggle to keep up).

I started trying to learn about potential insulation options back last spring, when we were having our roof replaced, because I wasn't sure if there was anything we needed to consider doing/installing while our roof was off. Ultimately, I have to admit that the more I read, the more confused I got, and we ended up just giving up on adding any insulation and just did a simple roof replacement. We've been considering blown-in insulation in the space above the attic ceiling (there's an open space above the attic ceiling, going up to the attic peak) but now I'm wondering if GibsonGM's comments regarding condensation on the underside of the insulation might be applicable to our situation as well where the upper attic space opens up to the walls..