Attic space insulation
I have friends who are renovating their 600 SF condo. They are on the top floor of a 4-story multi-unit residential building. The building is brick and completely uninsulated. I think it was built in the 1920’s.
There is a 3-1/2 foot cavity between their ceiling and the underside of the flat roof. On the side of the building within that “attic” space there are a few vents for free flowing air circulation. That “attic” space is contiguous above all the other condos. They asked me if they should insulate above their space.
My concerns are:
1. Because it is a multi-unit residential does the fire code limit the type of insulation they can use?
2. If they do insulate I would make sure we create an air barrier by sealing up all cracks,top plates,penetrations (maybe by flash foaming if allowed), It seems like it would be ok , but I know in some instances making insulation changes in a building like this affect the drying potential of the assembly. What do you think? We would still be allowing the existing venting to do its thing, but I am also worried that the other units will still be leaking their warm moist air into the space in the winter, which may permeate the insulation(depending on what we can use) Does anyone have any insight into this?
3. Does it even make sense to insulate the ceiling, given that the rest of the building in not insulated?
Thank you all………
David
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Replies
David,
1. Yes, it makes sense to insulate only one unit, even if the other units have uninsulated ceilings.
2. You always need to talk to your local building inspector before proceeding with any renovation that may have code implications. Local codes differ, so talk to your local building officials before settling on a plan.
3. I don't know of any reason why there would be code limitations preventing the use of spray foam to seal ceiling cracks.
4. Make sure that the insulation you install does not cover or interfere with existing ventilation openings.
Thank you Martin......yes I will check with the inspector about exposed foam,but if we end up with cellulose up there,do you think it could be subjected to too much moisture. From the other units?
David,
No, unless there is a roof leak.
Although it should produce decent energy savings for the unit that you insulate, it will increase the heat loss from the uninsulated units because the attic will get cooler. Some rough calculations indicate that the increased energy use in the other units might total to about one third or one half of the savings achieved in the insulated one. How about asking the neighbors if they want to get insulation too?
The units are all on one boiler fired steam system, and I believe there is only one zone.
David,
If the whole building is on one zone, how is the heating bill paid? Do all of the condo owners just split the bill?
If so, it's in everyone's interest to insulate the entire attic -- not just the ceiling of one unit.
I believe the heating bill is divided equally, and I would like to think this would be something the condo association would be interested in doing. We will see....thanks for all the input. David