Sealing and Insulating a Cathedral Ceiling and Attic

Larry Janesky, from Dr. Energy Saver explains the process of air sealing and insulating the cathedral ceilings and attic of newly constructed condominium units.

Air Sealing and Insulating

These are brand new condominiums and we've insulated according to the builders specification with fiberglass in the walls and we're going to be blowing the flat of the attic space with cellulose along with the rafter spaces in the cathedral ceiling.

Insulation Does Not Stop Air Flow

Now before we blow cellulose insulation in this attic we have to air seal which means we have to seal up all the places where air can get from the house up into the attic since insulation doesn't stop air flow.

Air Sealing

So what we want to do is seal places such as this where the drywall meets a top plate and this gap right here is a place where air can get from the wall cavity up into the attic, so if there was an electrical outlet in that wall the air could get into the electrical outlet and up.

Blown Cellulose Insulation

Now we're going to do is blow cellulose in this hose all the way down to the cathedral ceiling bays and we have air baffles all the way down to the bottom so that air from the vents could get up and out the ridge vent.

Read Full Transcript

Hi, I'm Larry Janesky from Dr. Energy Saver and today we're going to be insulating the attic and the cathedral ceiling slopes of this new home with blown cellulose. These are brand new condominiums and we've insulated according to the builders specification with fiberglass in the walls and we're going to be blowing the flat of the attic space with cellulose along with the rafter spaces in the cathedral ceiling. We've prepared for it by putting baffles in for the roof ventilation because it still will remain a vented roof and attic so all were going to do is stick the hose in to blow the cellulose down the rafter base from the attic, then blow the attic flat which will finish that part of the job.

Now before we blow cellulose insulation in this attic we have to air seal which means we have to seal up all the places where air can get from the house up into the attic since insulation doesn't stop air flow. Cellulose insulation will do a much better job than fiberglass insulation in stopping air flow but still we want to seal the dry wall to lumber connections and any holes in the lumber when we go up in the attic before we blow the insulation. Now in an existing home we have to move insulation to the side to find all of these leaks and then seal them which can be very difficult depending on the size of the attic, how much insulation is there, the type of insulation and if it's either very cold or hot up there. In this case it's a new construction so we have no insulation in the attic whatsoever it was just dry walled a couple of days ago.

So what we want to do is seal places such as this where the drywall meets a top plate and this gap right here is a place where air can get from the wall cavity up into the attic, so if there was an electrical outlet in that wall the air could get into the electrical outlet and up. Now over here we have a place where the electrician had drilled holes for wires to go down into the wall cavity and then seal around those wires so air doesn't leak up through the holes. Here we have a place where we have a duct going through the drywall and you see that his duct and the metal flange are not sealed to the drywall and what you have is an air leak from the interior of the house around the drywall, through the hole in the drywall and around the sheet metal flange then into the attic which would leak forever. Even worse than that is when the warm air is leaking out of the house and that's a powered air leak when the heating or cooling system is on. Now you have pressurized air going through here blowing air out of the grill that's going to be put on the ceiling but some fraction of that air is going to be a powered leak and blow out between metal and drywall into the attic, up through the insulation and be lost forever. These sheet metal boxes often have gaps and joints in them so I'm going to continue to fill all around this so there are no leaks, as we look around the electrical box we see a gap that will also leak forever.

There's going to be a ceiling light fixture on that underneath and the air will go into the light fixture, propel even more by the heat generated from the bulb in the fixture and it will leak out of this gap and through the insulation into the attic. Sealing this stuff may seem like a little thing now but when you consider the cost to pay to heat all the air that will leak through this hole for 100 years you'd think "Wow, it's worth it to pay to get it sealed now." It's so much easier to seal it now than to try to dig through the insulation to get this which is exactly what we have to do in existing homes. Now I spoke of this before as the builder sealed this up but he didn't do it, I guess he left it to us but here the top of a duct chase goes down in the supply and return ducts we're on all the way down to the heating system in the basement and you see this big hole.

Then that hole is going to let a lot of air up into the attic forever and also when we blow insulation in here our insulation is going to fall down in there so have to seal it with foam first. Now what we're going to do is blow cellulose in this hose all the way down to the cathedral ceiling bays and we have air baffles all the way down to the bottom so that air from the vents could get up and out the ridge vent. So 16 feet down this bay is how far we're going to shove this hose and fill the bay up then it will take about 3-4 minutes per bay and once we get all the bays done.

If you have any energy concerns in your home call Dr. Energy Saver, so we can help you make your home more comfortable and that includes every room in your home that should be comfortable in all seasons. We can help you have a healthier indoor environment and make your home more durable with less mold allergens.

Watch the Sealing and Insulating a Cathedral Ceiling and Attic Video or read about how Insulation can help make your home more efficient and more comfortable today