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Insulating walls and ceiling 1795 New Hampshire Colonial

I own a two story colonial in New Hampshire. I have started to removed the plaster and lathe from the interior to retrofit insulation. The exterior of the house is clapboards with aluminum clapboards over it. The exterior has no house wrap or tyvek type material. The interior walls or 2x4 rough cut. My question is about poly vapor barriers and sealing. Since the house has no house wrap it is drafty. I would like to stop this draft but not sure of the proper way to do it. I figured a polyvapor barrier attached to the studs as the last item before drywall would stop air infiltration. I have heard conflicting information though about the vapor and the way the building breathes. Should I or should I not use the poly vapor barrier? My other question is about how to insulate. Again with wanting to get a tight wall I had though about putting 1/2 polyboard in the stud bays against the exterior sheathing and sealing the edges with expanding foam. After that I would put a unfaced fiberglass batt of 3 1/2 inches over and finish with the poly vapor barrier. But again the whole building breathing is what has me wondering. Also someone before me has put poly sheathing d****d over the ceiling studs from the top in the attic and then placed fiberglass batts over that. Is this correct? Should I actually tear down the ceiling, attach a vapor barrier and then sheetrock it? I know this was long winded but I appreciate any help! Thanks.

Re: Insulating walls and ceiling 1795 New Hampshire Colonial

You live where you primarily heat. You don't have to do much, if any AC so it really simplifies things. You want the exterior walls to breath and a vapor barrier on the interior side of the exterior walls. Putting the poly board against the exterior sheathing and sealing it would be counterproductive.

If you want a layer of 1/2" polyfoam board, then use it as the vapor barrier over the fiberglass batts and over the ends of the studs. Be sure to tape the seams, use a closed cell spray foam in the seams or a 6 mil vinyl sheet over, then the sheetrock over that.

The advantage of using the polyfoam board over the inside of the studs is that it breaks the conduction path through the studs. The studs have a much lower R value than the fiberglass, so it will "short circuit" the heat around the insulation. At least 10% of your wall is studs.

When you put in the fiberglass, leave any gap on the outside so that you can get airflow on the outside of the insulation. Its the same principle as venting the attic. This will keep the fiberglass dry so it is a better insulator.

The best book for you would be "From the Walls In" by Charles Wing. The book is now out of print so new copies cost a pretty penny, but used copies are available at amazon and abebooks.com at a reasonable price. Charles Wing used to have a school called "The Wing School of Shelter Technology" that was located in Portsmouth or Bath, ME. (I don't know the area but I went to it once). Its about a block from Bowden College.

He co-wrote another book and that is available as a free download. It's about building a new house and it is interesting reading, but it doesn't address insulation for some reason.

I think your ceiling is ok, but that is not the best way to do it. BTW, You probably have ballon framing so the stud bay will run from the ground to the roof. If you have the gap against the exterior cladding, some vents in the bottom of the wall to the exterior and vent the tops of the stud bay into the attic, your walls will stay warm and dry.


Re: Insulating walls and ceiling 1795 New Hampshire Colonial

Thank you very much for your help!

So I like the idea of putting the fiberglass first(unfaced batts I assume?) against the exterior wall sheathing. After that, cover the interior wall with 1/2 Styrofoam as a thermal break from the studs with greatstuff in the seams. How would you attach to the studs, glue or screw? Next cover the whole wall with a 6 mil plastic sheeting vapor barrier. Any risk of the styrofoam boards cracking from screwing the sheetrock to the studs through the styrofoam?

As far as leaving a gap on the fiberglass you mean between the fiberglass and the exterior sheathing by holding it away from the sheathing in some way? Any suggestions?

As far as the balloon frame it is not, it is post and beam. There is a break from the first to second floor stud walls by the beam that crosses. Also same for the second floor stud wall to the attic, another beam that crosses at the top. So my stud bays don't have much air flow. Any ideas with this?

Lastly the attic, so the vapor barrier d****d over isn't the best but is ok? I really like the attic since it is full height and great storage. I would like to pull up all the floor boards in the attic, extend up the ceiling joists, fill with blown in cellulose then cover back over with the floor boards. Any thoughts on this? Thanks again for your help!

Re: Insulating walls and ceiling 1795 New Hampshire Colonial

Thank you for your help! I have a question about attaching the foam board to the studs, should I screw it? I am worried about the foam board cracking if I screw it to the studs as well as screwing through it to attache the drywall later. As far as the jiont I should just use greatstuff on the seam and then press them togeather? After that finish it off with the poly vapor barrier attaching it how and to where? Should I attach it at the top of the foam board, the ceiling where it meets the foam board etc?

Next about the fiberglass gap. Do you mean to hold the fiberglass off of the exterior sheathing somehow? If so any suggestions?

So the attic is ok with the vapor barrier d****d over the jiosts from the top? If so should I continue with my plan of extending the jiosts higher so that I can blow in loose cellulose ontop and then cover back over with floor boards.

Lastly the house is post and beam construction, not balloon frame. There is a beam that runs around between the first and second floor in the stud bay. Same thing from the second floor to the attic, another beam that runs around so the stud bays are seperated. Any suggestions with this ? Thanks again!

Re: Insulating walls and ceiling 1795 New Hampshire Colonial

If you are going to use a poly vapor barrier, you do not need to seal between the sheets of foam board. In fact. it might be counter productive as you really do not want two vapor barriers, you only want one.

As for the fiberglass, just don't press it into the cavity very hard. But you may run into other issues, I have heard that in those old post and beam houses, the stud bays are not regularly spaced. Using a stand width fiberglass batt might be difficult. To make a gap on the outside, there is a plastic product that is often used in the rafters of Cape Cod houses to space the insulation away from the roof. You could use that in the walls.

You attach the poly vapor barrier all around the wall, and around all the windows. I would avoid stretching it tight as it will expand and contract with the temperature, but since it is on the inside of the insulation, it won't do this too much. The sheet rock will hold it in place.

The foam insulation boards will not need many screws or nails either, again the screws or nails for the sheetrock will hold them in place, just be sure to use the longer screws or nails. You will want inch and 3/4 instead of the usual inch and 3/8ths. You could use inch and 5/8ths if need be.

For the attic, consider running the joist extenders perpendicular to the joists. This will reduce the conduction area of the wood in your ceiling. Fill that in and then run your floor boards. If you don't need the attic storage space, then just blow insulation right over the tops of the ceiling joists.

Re: Insulating walls and ceiling 1795 New Hampshire Colonial

to hold the insulation board while working, a dab or two of liquid nail works wonders. be sure to put small lines to mark studs on roof and floor so they can be easily and quickly located to nail wallboard.

Re: Insulating walls and ceiling 1795 New Hampshire Colonial

I'm having second thoughts on that attic vapor barrier being laid (d****d) over the tops of the joists, it might hold moisture to the joists and cause rot problems down the road. You may not really need any vapor barrier up there at all so it may be best just to remove it.

Attics tend to be well ventilated, unlike walls, so having no vapor barrier usually does not present a problem. The adequate ventilation will remove any vapor that migrates into the insulation up there so condensation usually does not occur.

What you do want to do is caulk around any light boxes so that air does not enter the attic around them. This is one area of heat loss that is often overlooked, and it is significant. Likewise, you should caulk around any switch and outlet boxes that are in your exterior walls.

If you have a wet wall on the second floor, thats two walls back to back with plumbing run between them, often one of the bathroom walls, check that this doesn't have an open top in the attic. If it does, bridge the opening with Tyvec and insulate over that. Be sure to seal any vent pipes in the attic and insulate around them. You would be surprised at the heat loss they account for.

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