Replies

1. 
   maine_tyler | Nov 19, 2019 06:39pm | #1

   David,
   Someone with more authority will hopefully weigh in, but I believe there are some concerns with your exterior drying potential. Double stud walls typically rely on outward drying.

   I'm not sure of the exterior siding detailing, but aluminum and brick don't sound too good in this regard.
   It may be worth working from the outside and building in a rain-screen. If you're already tearing up the outside, you could also consider exterior insulation (foam/rockwool) as a viable (maybe better?) option.

2. 
   walta100 | Nov 19, 2019 07:14pm | #2

   Before you blow insulation into a wall you need to be sure there is no knob and tube wiring in the wall.

   1952 probably no K&N but still double check as it is a fire safety issue.

   The other thing to worry about is keeping the insulation dry. Without insulation if your window flashing leaked a little there was plenty air moving thru the walls to dry the wood before mold or rot could get going. The problem is now you go and air seal and fill the walls with fluffy stuff that will soak up the water and never dry and it becomes a rotten moldy mess. You may want to open the walls around a window or 2 and see if anything look like it may have been wet. Another place the insulation can get wet often the siding was nailed directly to the 2x4s without sheeting or tar paper so if the original siding gets wet the insulation could get wet. Again open up a hole or 2 and see what you have you may have 4 different waterproof layers or you may have none. You will never know until you look and no two wall may be the same.

   Walta

3. 
   onacurve | Nov 19, 2019 07:59pm | #3

   Thanks very much for the answers.

   There's no knob n tube. I'm sure of that.

   I don't think any windows have leaked. I haven't seen evidence of that.

   I'm not going through the brick to insulate from the outside because the mortar joints are so small that I couldn't fit a flexible insulation tube through the hole.

   I will be doing this from the interior.

   I saw some old photos of the brick going up. My memory isn't the best but I think I saw the old aluminum siding in place as the brick was laid.

   I think an interior vapor barrier would be a big mistake, from what I've read, so I won't be doing that.

   Thanks again.

1. Expert Member
   MALCOLM TAYLOR | Nov 19, 2019 09:46pm | #4

   David,

   I think you will be fine. Spend a bit of time air-sealing the existing drywall. It should be easy as you can use any method you want as it will get covered.

   One complication may be the electrical. Our code wouldn't let you bury the old boxes, or use them as junction-boxes unless they were accessible. I'm sure it's not something insurmountable with a bit of planning..

1. Expert Member
   BILL WICHERS | Nov 20, 2019 01:57pm | #6

   Our code doesn’t allow inaccessible junction boxes either. They don’t have to be “easily” accessible though, so a tight spot in an attic or crawlspace is fine. It just has to be physically possible to get to them if you really need to.

   If you have the walls open, I’d replace ALL the knob and tube in those areas. It’s not hard to run new NM cable in the same holes the old through-stud insulators (the “tubes”) used. This has the benefit of giving you a good electrical upgrade, getting you a ground wire everywhere for grounded outlets, and upgrading the wire gauge since some old K&T wiring was relatively light gauge wire.

   I’d also recommend using at least 12 gauge wire for all receptacle circuits. Only use 14 gauge for lighting circuits. That’s not a code requirement, but it’s good practice.

   Bill

4. Expert Member
   Dana Dorsett | Nov 20, 2019 01:23pm | #5

   What type of exterior sheathing is under the aluminum siding layer?

   Is the brick veneer vented to the exterior with weep holes at the bottom and vents at the top?

5. 
   onacurve | Nov 20, 2019 05:41pm | #7

   Hello and thanks for the responses.

   Dana, I don't know what type of sheathing is behind the aluminum siding. There are weep holes at the bottom. I haven't seen vents at the top. If they exist, they aren't obvious. Maybe they are above the soffit.

   Here's a photo of part of an exterior wall, if it's helpful.

   
6. Expert Member
   Dana Dorsett | Nov 20, 2019 06:37pm | #8

   Sometimes the masonry cavity gets vented into the attic or soffits (not great, but works OK if well vented.) Adding vents in the top course of brick corresponding to the weeps below (but staggered, to keep falling debris from drilling out the vents from blocking the weep) would be a good idea, especially if there is no path to drying via the soffits. Since the brick was an afterthought it's unlikely that the cavity is vented into the attic.

   In my area it's standard practice to install weeps & vents every 3rd or 4th brick- yours looks like every 6th, but with deep roof overhangs like yours it's probably not as critical, since saturating wind driven rain wetting events that could soak much of the wall are probably very rare.

   If it's fiberboard sheathing it would preclude dense-packing the walls. If it's 1x ship lap or t & g planking it's probably not a problem and if it's plywood DEFINITELY not a problem. But it will take some archeological probing to find out. If there is a closet or cabinet space where you can cut out a square foot of drywall, or even a 3" hole with a hole-saw you can probably figure it out pretty quickly. Drilling a smaller hole/coring through the sheathing would be enough to tell if the aluminum siding is still in place, and determine the depth of the masonry cavity, and the type of weather resistant barrier, if any.
   There is probably a layer of #15 felt/tar-paper, if the sheathing is plank or plywood, probably nothing if the sheathing is asphalted fiberboard. But it's necessary to know the complete wall stackup before insulating the cavities to avoid any pitfalls, and it will affect what insulation type/density makes the most sense. (Sometimes 1lb fiberglass is the "right" solution, despite it's poor air-retardency.)

7. 
   onacurve | Nov 20, 2019 10:52pm | #9

   Thank you so much, Dana. I really appreciate the advice.

   I'm planning on getting started over the holiday weekend. I might post some comments and photos to let you know what I find out.