Topic: 95 Year Old House Remodel - Any Insulation Experts?

[CBJoe]

I feel like this is gonna be a build thread for my house 

My house is a small cottage built around 1925.  It's a 1.5 Story with a lot of character.  At this point there isn't a wall cavity I haven't probed for one reason or another.  I did a full rewire about 10 years ago as the old cotton wire BX Cabling was rotting out. Ran new wire throughout myself and then had it checked out by an electrician when I had my service upgraded and a new panel installed...passed muster thank god...handyman work but good enough 
 
The "upper" story is a single room 9' x 28' room which was our bedroom.  Low ceiling and lots of unused space above and to the sides.  We have been planning to gut and blow out the upstairs and add a bathroom for many years...well..the time has come

We've moved down to the living room where I built a temporary door to close me and the missus off from house guests...pretty proud of my redneck engineering.  Padding between the 2x4s and no screws into the archway....can take it all down in < 15 minutes.





I got a buddy to help me tear the upstairs out this weekend.  Was an exhausting few days...rented an insulation vacuum and a big waste dumpster.  I'm off the next 2 weeks to finish the tear out and make some headway.  I give myself about 3 months to finish the project...my friends are taking bets on it being more like 6 

[CBJoe]

So now to my insulation question.

I'm removing the entire room framework that is there now and will install 4' Knee Walls.  I'm planning to do a shiplap or T&G cathedral ceiling with insulated rafter spaces. Problem I have now is that my rafters are only 2x6's.  That doesn't leave a lot of room for insulation.

So...do I install/make Rafter Baffels or do I close off the ridge vent and make the rafters unvented?  Would love some input from others who know the trade better than myself.

To be clear...I had < 4" of insulation prior to this remodel.  So whatever I end up with is better than what I had.  I can fur the rafters out to allow for more depth and therefore more insulation space.  BUT ....what I'm trying to decide is if I should do Vented Rafters or unvented. 





My roof has 1 layer of asphalt shingles (which was not leaking at the time) and a metal room installed over top of it.  They essentially cleaned the roof and put down a vapor barrier and then 2x2 (I think) horizontally across the roof.  The Metal panels then screwed down to those 2x2's.  So there is some air gap between the roof and the panels.  Full Ridge Vent across all.







Cheers, Joe

[Don R]

 Since you don't have asphalt shingles on the top, that reduces the need to ventilate the underside of the roof. A cold roof is better but that's not really going to work.
 I think rock wool is higher r value than fiberglass per inch, check that out. See if local codes cover R values.

[CBJoe]

Open cell foam. Spray it yourself and fill the rafter bay. You'll get 5.5" of insulation, and a much higher R value than fiberglass batt.

Hi Cal...I totally agree with you on the R-Value advantage about the spray foam, but unfortunately my wife has major smell/migraine sensitivity to off-gassing of some foam products.  We have a number of friends that have had this done in their attic/loft conversions and she still gets some irritation from being in the spaces for too long.  I'm sure this doesn't apply to all situations but we just aren't wanting to risk it.

Since you don't have asphalt shingles on the top, that reduces the need to ventilate the underside of the roof. A cold roof is better but that's not really going to work.
 I think rock wool is higher r value than fiberglass per inch, check that out. See if local codes cover R values.

Hey Don...Rockwool is what I was planning to use in combination with closed cell rigid foam.  I used rockwool in my garage and was very pleased with it. 

I actually just found a good article which covers a lot of the topics that I was mulling over.  https://www.greenbuildingadvisor.com/article/how-to-build-an-insulated-cathedral-ceiling

What I'm considering at the moment is 2" of Rigid Closed Cell foam directly under the roof sheathing with the edges sealed (R10).  Then Fur out the rafters by 2" which will let me put around an R24 of Rockwool.  This will give me R-34 in total which doesn't meet new construction code.  But to my understanding the there are loopholes for old house remodels to either bring to code or at a minimum to the maximum the existing structure allows.  It will be impossible for me to meet new construction code in this old house.

I've got a bit to mull over options.  Thanks for any input.

Joe

[demon78]

I tend to agree with Cal but I'd use the net to look at problems of that type of construction if I remember your national building center has info on that if not check out our NRC, how cold does it get where your at ? The other thing talk to a contractor that does foam they can from experience tell you what's required. If your wife has a problem I think you are stuck with rock wool
Bill the demon.

[CBJoe]

I tend to agree with Cal but I'd use the net to look at problems of that type of construction if I remember your national building center has info on that if not check out our NRC, how cold does it get where your at ? The other thing talk to a contractor that does foam they can from experience tell you what's required. If your wife has a problem I think you are stuck with rock wool
Bill the demon.

Hi Bill...I live in Indianapolis, so it can get pretty cold.  To be honest If I get my R Value up to 34 it's about R-20 more than what I had 

[pmanning]

It is hard to tell from the photos but it seems to me that the exposed ceiling framing also serves as rafter ties.  If that framing is removed then some alternate structural framing may be needed to replace their function.  With essentially two roofs on the house it could be a consideration.

Insulation behind the 4' knee walls can be as thick as you want.  Also in these type renovations it is common to flat roof a section of the ceiling near the peak.  That would also allow for thicker insulation there.

[CBJoe]

It is hard to tell from the photos but it seems to me that the exposed ceiling framing also serves as rafter ties.  If that framing is removed then some alternate structural framing may be needed to replace their function.  With essentially two roofs on the house it could be a consideration.

Insulation behind the 4' knee walls can be as thick as you want.  Also in these type renovations it is common to flat roof a section of the ceiling near the peak.  That would also allow for thicker insulation there.

The Ceiling joists in the current room do not act as rafter ties....they are not even attached to the rafters at all and are just toe nailed to the top plate of the walls.  The First Floor Ceiling Joists act as the rafter ties and currently there are no collar ties.  To my understanding Rafter Ties are in the lower 1/3 of the rafter span and Collar Ties are in the upper third.  Here’s a pic of the ceiling joists up there...you can see they are not tied to the rafters



Like you mentioned, I'm going to be adding Collar Ties to act as a flat spot to mount the flat ceiling section.  And you are correct...I will have thicker insulation for that top area.

My big decision at the moment is vented or unvented rafters.  I'm leaning towards unvented since I've got the metal roof with an air space between it and decking.

Thanks for calling anything out I may have missed...kind of why I stared this thread to make sure I’m not missing anything silly.

Cheers, Joe

[Stev-o]

+1 open cell insulation.  As a project manager, that is all I use on my projects except when using R12 batt for sound on interior walls.

Contact a local expert, there are low VOC options...

[CBJoe]

Thanks all for the input...I'll reach out locally to discuss some options/methods.  I have quite a bit of work to do before I solidify a method.

I'm also tearing out and replacing my soffit and fascia while I have easy access from the inside and out.   have a feeling quite a few rafter tails will need to be sister'd due to rot.
 

[Spanner 1]

The ceiling joists in your pic are what hold the walls from spreading under the roof load, i.e. the roof rafters trying to 'spread' the roof out. Be sure to add collar ties first before removing any ceiling joists. Also if you care about codes then the rafters will need to be scabbed out to 2x12 allowing R-30 insulation against baffles from soffit to ridge and ridge needs to be ventilated . Codes, damn !

[BigJimG]

+1 open cell insulation.  As a project manager, that is all I use on my projects except when using R12 batt for sound on interior walls.

Contact a local expert, there are low VOC options...

Why open cell vs closed?  Cost?  When I remodeled the rooms on the west side of my house, I used closed cell and a full fill, figured the higher R-value and sealing capabilities was worth it on the prevailing side of the house.

[CBJoe]

The ceiling joists in your pic are what hold the walls from spreading under the roof load, i.e. the roof rafters trying to 'spread' the roof out. Be sure to add collar ties first before removing any ceiling joists. Also if you care about codes then the rafters will need to be scabbed out to 2x12 allowing R-30 insulation against baffles from soffit to ridge and ridge needs to be ventilated . Codes, damn !

Hi Spanner...if you look at one of my posts above you will see this room was free standing and did not serve any load bearing or roof support purposes.  The Walls Top Plates made ZERO contact with the Rafters (top plate was notched around rafter), and the ceiling joists also had no mechanical connection to the rafters.  They were just toe nailed onto the top plate.  This room was built sometime between 1930 and 1945 (but it may have been framed when the house was built and finished later.

Cheers, Joe

[Duke McDukiedook]

Hey Joe, what is the spacing on those 2x6 rafters? Is it 24" OC?

[CBJoe]

Hey Joe, what is the spacing on those 2x6 rafters? Is it 24" OC?

Yes

[Duke McDukiedook]

What is the slope on your roof? About 1:1 or a little less?
What is the rafter span on that roof? (length of your lower ceiling joists)

The reason I ask is 2X6 rafters at 24" spacing is getting a little out there depending on your rafter span based on your pitch. If you just had the one asphalt shingle layer it would probably not be a big deal, it just depends on how much that metal roof on top of it weighs.

[CBJoe]

What is the slope on your roof? About 1:1 or a little less?
What is the rafter span on that roof? (length of your lower ceiling joists)

The reason I ask is 2X6 rafters at 24" spacing is getting a little out there depending on your rafter span based on your pitch. If you just had the one asphalt shingle layer it would probably not be a big deal, it just depends on how much that metal roof on top of it weighs.

Hey Dukie,

It’s a 12:12 pitch with appx 11.5ft joist/rafter span.  Thats the span from edge to the main center support of the house.  All this will be double checked before doing the work. According to the manufacturer at install the metal roof weighs less than an asphalt roof.  I actually called the roofing company and confirmed the weight of the roof I have is around 150lbs per square.  A lot less than most shingles. 

The plan at the moment is to put knee walls in down the length of the room on either side to provide some support against sagging, but the dead load I’m going to be adding on the rafters should be pretty minimal.  I’m actually doing some research on that whole topic now. Luckily I have some friends that have some resources that can help check me on it before doing anything.  I've got a 3 month goal to completion this project...so plenty of time.

Luckily the bones of this house is all old growth framing lumber from 100 years ago.



Joe









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[Duke McDukiedook]

It sounds like you should be okay.
I just get a little worried when I see 2x6's spaced out that far because I saw that on my FIL's roof with a few layers of shingles.

[Spanner 1]

Wow CB Joe… got it ! So the upstairs framing was obviously done later, interesting how its not even tied to the roof rafters !

[CBJoe]

Wow CB Joe… got it ! So the upstairs framing was obviously done later, interesting how its not even tied to the roof rafters !

Haha!  Trust me...I was pretty happy when I saw that it was free standing.  Made it much easier as I can open the whole space up to shore up and design the new layout without having to worry about interim bracing.  House stood for this long without bracing it can do so for a bit longer

Joe


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