Replies

1. 
   Andrew_C | Apr 13, 2023 05:06pm | #1

   Initial thoughts - don't install pot lights, use surface mounted LEDs. There are a lot of Q&As and a few articles here on GBA on this topic.
   It's not clear what the spacing is from your picture, but generally I take a piece of plywood up in the attic with me that's wide enough to easily span adjacent bottom chords. This makes it easier to kneel and avoids stepping thru the ceiling, which is a terrible way for deciding where to add lighting ;)

1. 
   tkzz | Apr 17, 2023 03:34pm | #6

   Thanks Andrew, pieces of plywood make sense.
   The space is pretty tight... both upper and lower spaces are only big enough for crawling!

   I was thinking recessed LEDs actually... but even a surface mounted LED would require a 4" hole for the junction box no?

2. 
   walta100 | Apr 14, 2023 11:46am | #2

   I would avoid spending a lot of time in that attic.

   I would focus my air sealing efforts inside the conditioned spaces. Blower door directed air sealing would be a good start. Getting a blower door test is not what you want. You want them to test you house several times using its fan to find the leaks caulk the leaks and test again over an over all day long. They will never get all the leaks so you need to set some limits in terms if hours /dollars or if they somehow get under 2 ach50 very unlikely.

   I see air sealing as a good DIY project tape a box fan into a window and use the smoke from incense sticks to find the leaks and fill them with caulking.

   Walta

1. 
   tkzz | Apr 17, 2023 03:32pm | #5

   Thanks Walta I am not sure if I can find the time to do that myself but if I do and I find some leaks in the ceiling electrical boxes for example (these are the only spots where there are holes in the ceiling), how would I seal them from the conditioned space?

1. 
   walta100 | Apr 28, 2023 01:53pm | #9

   Yes, I would caulk from the room side any place I could detect air movement with smoke.
   Paintable caulk this is the one I used a lot of.

   https://www.lowes.com/pd/Big-Stretch-10-5-fl-oz-White-Paintable-Latex-Caulk/4411173

   Caulking any gaps between the fixture and the ceiling and over holes next to the mounting screws is safe but a pain if you later need to remove the fixture. Caulking inside the box that would displace air should be avoided as the air space is needed to keep the wires cool. Caulking in a box with live wires would be dangerous. Filling all the holes in the box from the inside could be done but sealing the outside of the fixture sound easier.

   Walta

3. Expert Member
   BILL WICHERS | Apr 14, 2023 02:00pm | #3

   It looks like you have blown fiberglass insulation in place now. It also looks like, but is difficult to tell for certain, that your can lights might be "boxed over" on top, in which case they may have already been air sealed? If the basic air sealing work has already been done, and you don't have to worry about covering up anything, it would be easy to blown in additional cellulose over the top of the existing fiberglass to bring your total insulation value up to your target R value. Cellulose is a little better at resisting air movement compared to fiberglass too, so it will help a little if your air sealing isn't ideal.

   I agree that doesn't look like a fun attic to work in, but in my experience, there are NO attics that are fun to work in -- they are ALL miserable.

   Bill

1. 
   tkzz | Apr 17, 2023 03:21pm | #4

   Thanks Bill. I actually don't have any can lights, what you are seeing are scraps of plywood and shingle, I'm guessing from the previous owner's last roof job. I was thinking of adding some recessed led lights and sealing those accordingly, before topping up the insulation.

   It sounds like you're suggesting adding cellulose over old fiberglass as opposed to adding more fiberglass. Is this best practice? As I did not do the original insulating job (it was a previous owner...probably 20+ years ago), would I gain anything by lifting out some of the old insulation to inspect the sealing etc or should I just cross my fingers and leave it?

   cheers

4. Expert Member
   Akos | Apr 17, 2023 09:17pm | #7

   The hard part will be to get planks up there to get around. Once you get some wood over the ceiling joists, it should not be too difficult to get around. Not fun, but no that hard. With older fiberglass insulation, I would recommend one those Tyvek suits and good dust mask. A respirator seems like overkill but I find it much easier to breath through. You also want a bike helmet (or eqivalent low profile helmet with straps) to avoid getting stabbed in the scull by roofing nails.

   You'll have to move some of the insulation around to get access to your top plates to air seal. Sometimes these older houses have some ugly details where an interior wall cavity is completely open to the attic, make sure to seal up anything like that. Some baffles (every 2nd bay is usually good enough) by the soffit is a good idea if adding a lot of fluffy. One of those spray foam guns makes lot of this work much easier.

   For sealing the pot lights, this might help:

   https://www.greenbuildingadvisor.com/question/how-to-air-seal-a-slim-led-light

   You can do something similar over the existing ceiling devices boxes as well.

   Finally, do this on a cold day, not in the middle of summer.

1. 
   tkzz | Apr 28, 2023 12:03pm | #8

   Good tips, thanks Akos!