Home & Garden

Sealing Duct work

  • Last Updated:
  • Dec 21st, 2018 1:36 pm
Tags:
Deal Addict
Sep 12, 2017
2483 posts
284 upvotes

Sealing Duct work

Have a new 1600 sqft home with a basement, 1st floor, and 2nd floor. With new ecobee temp. sensors installed on each floors, I've noticed the basement is is the warmest level in the house with a single degree being lost every time we move up a floor. Planing to seal the duct work in the basement via foil tape and mastic if I could find some in GTA. I'd like to participate in shop-the-block AM promo and was hopping to buy some foil tape from rona.
1. Are any of these foil tapes better then others?
2. Where does one get mastic in the GTA, no big box stores carry them, at least online when I checked. Is it needed or is foil good enough on all seams?
3. Is any of this reflective insulation at Rona good for adding insulation to duct work? From the description it sounds like it just bubble wrap, should that not be proper fibreglass insulation around the HVAC duct work instead?
25 replies
Deal Fanatic
Nov 18, 2005
5111 posts
1546 upvotes
Kitchener
Amazon sells Red Devil duct sealant, and 3M 4.0mil foil tape. I don't know how to paste a link from the Amazon app
Deal Expert
Jan 27, 2006
21844 posts
15620 upvotes
Vancouver, BC
While all foil tape looks the same, they ain't... while they all do essentially the same job (ie tape things together), some tapes are harder to use than others as the wax paper backing is harder to peel off. I've found that the cheapest stuff is generally harder to peel but that doesn't matter to you, then just get the cheaper stuff. I've never had any 'fail' over the years once applied.

If you are noticing a drop in temperatures, before you do too much work, have a look at the ducting baffles as well as the cold air return vents. Often the system isn't balanced so adjusting the baffles may help as each floor's or group of floors' airflow is generally controlled by a baffle in the ductwork. Also, verify that you are getting some cold air returned on all of the floors. Many times the floors closest to the furnace get the most air returned while the upper floors get none. You may need to partially seal off some of the cold air return vents on the lower floors to get enough air returned on the upper floors.
Deal Expert
User avatar
May 10, 2005
36997 posts
11419 upvotes
Ottawa
Using foil tape is good but mastic is better.
One thing with foil tape is that for it to firmly stick and seal, you must burnish it.
I have an older house and have run the gamut trying to even out the temperatures in my house. Your "problem" of one degree differential between floors is as good as it gets. While trying for perfection, your house is way better than any I have ever heard of and you should be extremely happy.
Oh and, never ever seal off cold air return ducts. They are absolutely necessary for air circulation. If anything, close down the air vents entering the rooms.
“Those people who think they know everything are a great annoyance to those of us who do.”
Deal Fanatic
Nov 17, 2012
5381 posts
4997 upvotes
Toronto
I'd love to have 1 degree difference from floor to floor :)

1910 three storey house with a finished basement. Warm and toasty down there with the furnace and duct work radiating heat, then many degrees cooler on the 3rd floor. Nest thermostat on the main floor.

There's no fighting it, so I have a couple of the oil filled radiator heaters for the cooler spots in the house, and a portable a/c unit for the 3rd floor which gets very hot in the summer with it's flat, poorly insulated roof. No attic space to speak of.

Definitely seal your duct work - that should have been done when it was installed. It might help a bit but I wouldn't spend too much time or energy fighting for a degree here or there.
Sr. Member
User avatar
May 22, 2012
834 posts
459 upvotes
Toronto
Is there a reason big box stores don't carry mastic in Canada? I had to pickup some in the US
Deal Addict
Sep 12, 2017
2483 posts
284 upvotes
Drthorne wrote: Amazon sells Red Devil duct sealant, and 3M 4.0mil foil tape. I don't know how to paste a link from the Amazon app
Thanks for sharing. Any idea what these "UL 181 A-P and UL 181 B-FX printed backing for HVAC systems" ratings mean? Also does the foil tape have a mastic\rubber backing or is it simply glue. Just wondering what is best for it to hold up over the years.
Pete_Coach wrote: Using foil tape is good but mastic is better. If anything, close down the air vents entering the rooms.
Just though warm air rises and it be warmest in the 2nd floor bedrooms not the basements. Which led me to believe no all the duct joints\seams are sealed, and they are not. Hindsight should up taped up the duct work when the house was being constructed, after-hours.

Would you use mastic then tape on top of the mastic once it dries, or is it one or the other basically?
Being a small 1600 sqft home, would you recommend closing any of the basement vents in the winter? Or should one be closing some unused bedroom vents upstairs in the winter as warm air should be rising up from the lower levels?
torontotim wrote: I'd love to have 1 degree difference from floor to floor :)
Definitely seal your duct work - that should have been done when it was installed. It might help a bit but I wouldn't spend too much time or energy fighting for a degree here or there.
Well this is a 2017 home, sure some things changed over the 100 years, :). Duct work is sealed with foil tape, but they don't touch any of the seams, which also leak.

Any thoughts on insulating the duct work? Rona just shows some reflective bubble wrap duct insulation, would not fibre-glass insulation be better?
Deal Fanatic
Nov 17, 2012
5381 posts
4997 upvotes
Toronto
reggyDeal wrote: Duct work is sealed with foil tape, but they don't touch any of the seams, which also leak.

Any thoughts on insulating the duct work? Rona just shows some reflective bubble wrap duct insulation, would not fibre-glass insulation be better?
Not sure what you mean by the foil tape not touching any of the seams? That's the only place foil tape would be - on the seams between sections of duct work. The more insulation the better to avoid heat loss along the ducts before the warm air gets into the room it is intended for.
Deal Expert
User avatar
May 10, 2005
36997 posts
11419 upvotes
Ottawa
reggyDeal wrote: .....
Just though warm air rises and it be warmest in the 2nd floor bedrooms not the basements. Which led me to believe no all the duct joints\seams are sealed, and they are not. Hindsight should up taped up the duct work when the house was being constructed, after-hours.

Would you use mastic then tape on top of the mastic once it dries, or is it one or the other basically?
Being a small 1600 sqft home, would you recommend closing any of the basement vents in the winter? Or should one be closing some unused bedroom vents upstairs in the winter as warm air should be rising up from the lower levels?


.......

Any thoughts on insulating the duct work? Rona just shows some reflective bubble wrap duct insulation, would not fibre-glass insulation be better?
Mastic is used stand alone. Do not add foul tape over it. Mastic will remain somewhat flexible for the expansion and contraction of the ductwork. My preference is mastic and is permanent.
As I mentioned, I have done the mastic, foil tape and more but still "balance" my ducts for summer and winter. The air that is "forced" through the vents in summer is very different than the air in winter. Simply put, hot air rises (because it's drier and lighter) and cooled air falls (because it is heavier and full of moisture). So, opening the vents and ducts in areas that need the particular airflow is wise.

It is not necessary to insulate the ductwork. Most of it is inside the walls already and the bit that is exposed will also conduct heat into the area.
“Those people who think they know everything are a great annoyance to those of us who do.”
Sr. Member
Dec 4, 2009
837 posts
875 upvotes
Flamborough
Noble Trade sells the mastic, however, they might tell you they only sell to contractors....

Ask nicely and they may complete a cash sale...
Deal Guru
Jul 7, 2017
10214 posts
5528 upvotes
SW corner of the cou…
You could try a real plumbing supply store (such as Andrew Sherret(sp?) out in B.C.). I've never asked for mastic there.

I'm tempted to insulate the main trunk duct of my house as I have a heat pump and the air temp isn't very warm to begin with.
I smile when I see container ships sailing past my house laden with stuff made in China
Deal Expert
User avatar
Feb 11, 2007
21246 posts
25711 upvotes
GTA
Don't bother insulating interior ducts. Just make sure they're sealed in the basement with foil tape or mastic.
If you have vents in the basement, close them to redirect the air to the top.
You can also keep your HVAC fan running to circulate air and even out the house.
If the women don't find you handsome, they should at least find you handy.
Deal Fanatic
User avatar
Dec 11, 2005
9870 posts
1914 upvotes
TO
Pete_Coach wrote: Mastic is used stand alone. Do not add foul tape over it. Mastic will remain somewhat flexible for the expansion and contraction of the ductwork. My preference is mastic and is permanent.
As I mentioned, I have done the mastic, foil tape and more but still "balance" my ducts for summer and winter. The air that is "forced" through the vents in summer is very different than the air in winter. Simply put, hot air rises (because it's drier and lighter) and cooled air falls (because it is heavier and full of moisture). So, opening the vents and ducts in areas that need the particular airflow is wise.

It is not necessary to insulate the ductwork. Most of it is inside the walls already and the bit that is exposed will also conduct heat into the area.
I was going to ask the same, what if you have a finished basement and duct work is not exposed anymore? I remember before it was exposed we checked the seams and there was no loss of heat but not sure if that changes overtime.
"You can't soar with the eagles if you're hanging with the turkeys - Gary Kent
Deal Expert
User avatar
Feb 11, 2007
21246 posts
25711 upvotes
GTA
TorontoEh wrote: I was going to ask the same, what if you have a finished basement and duct work is not exposed anymore? I remember before it was exposed we checked the seams and there was no loss of heat but not sure if that changes overtime.
Loss of heat to leaks in the house don't lower your home's efficiency, but they can be a problem if the air isn't getting to where you want it, like vents that are far away. If you do have big leaks that you want to fix, the easiest way is using Aeroseal, where they spray sealant into your system, but it's costly ~$2-3k.
If the women don't find you handsome, they should at least find you handy.
Deal Expert
User avatar
May 10, 2005
36997 posts
11419 upvotes
Ottawa
TorontoEh wrote: I was going to ask the same, what if you have a finished basement and duct work is not exposed anymore? I remember before it was exposed we checked the seams and there was no loss of heat but not sure if that changes overtime.
If the ducts are covered and you have no access, then you will not be able to balance the ducts ether and that can be problematic.
engineered wrote: Loss of heat to leaks in the house don't lower your home's efficiency, but they can be a problem if the air isn't getting to where you want it, like vents that are far away. If you do have big leaks that you want to fix, the easiest way is using Aeroseal, where they spray sealant into your system, but it's costly ~$2-3k.
In a long ago thread I went through all the things I did to get my house comfortable.
In the end, after doing all the normal things, I got an Aeroseal treatment done. It is not a panacea for the air circulation problems. In the end, my house is much more comfortable in all rooms but, i still have to balance the airflow each spring and fall.
Aeroseal may be the only real option for those that do not have access to the ducts but, they will still have to open and close vents in each room to get airflow.
I also suggest leaving the furnace fan on all the time. This will make sure there is continuous airflow throughout the house at all times.
“Those people who think they know everything are a great annoyance to those of us who do.”
Deal Fanatic
User avatar
Dec 11, 2005
9870 posts
1914 upvotes
TO
Pete_Coach wrote: If the ducts are covered and you have no access, then you will not be able to balance the ducts ether and that can be problematic.


In a long ago thread I went through all the things I did to get my house comfortable.
In the end, after doing all the normal things, I got an Aeroseal treatment done. It is not a panacea for the air circulation problems. In the end, my house is much more comfortable in all rooms but, i still have to balance the airflow each spring and fall.
Aeroseal may be the only real option for those that do not have access to the ducts but, they will still have to open and close vents in each room to get airflow.
I also suggest leaving the furnace fan on all the time. This will make sure there is continuous airflow throughout the house at all times.
Pete, I've heard about running it constantly and all-day fan but do you think apart from the hydro bill, there are any other consequences? The fan/motor will have to work harder if its not stopped for a period of time. Right now, mine comes on during each heating event and I have a schedule setup in my Nest app to run it frequently throughout the day.

I do notice the temp of the home does go up .5 to 1 full degree if fan is on and circulating for a couple of hours but then I always worry about if if my fan motor blows or other components fail?

I don't even know if I have a Hi Eff furnace and if/or it's 1 or 2 Stage like they say now a days. I do use a 3m high merv rating filter (we had some construction done in basement recently) so I was told to use this to capture all dust/particles etc.
"You can't soar with the eagles if you're hanging with the turkeys - Gary Kent
Deal Guru
Feb 9, 2006
13377 posts
8308 upvotes
Brampton
TorontoEh wrote: Pete, I've heard about running it constantly and all-day fan but do you think apart from the hydro bill, there are any other consequences? The fan/motor will have to work harder if its not stopped for a period of time. Right now, mine comes on during each heating event and I have a schedule setup in my Nest app to run it frequently throughout the day.

I do notice the temp of the home does go up .5 to 1 full degree if fan is on and circulating for a couple of hours but then I always worry about if if my fan motor blows or other components fail?

I don't even know if I have a Hi Eff furnace and if/or it's 1 or 2 Stage like they say now a days. I do use a 3m high merv rating filter (we had some construction done in basement recently) so I was told to use this to capture all dust/particles etc.
They (Contractors and manufacturers) say starting and stopping is hardest on a motor.
Either way motors all have a finite life span. Sometimes it's not the motor but the capacitor on a PSC motor.
My Parents house only ran their fan when the HVAC was on cooling or heating. Lasted ~15 years. My neighbour runs his fan 24/7 It's over 13 years now.
Just know you shouldn't pay more than $300 for an PSC motor or $500 for a ECM.

If you have an ECM motor it costs pennies to run a fan 24/7. Or you can upgrade your PSC motor to an ECM to take advantage of lower power consumption.
Deal Expert
User avatar
May 10, 2005
36997 posts
11419 upvotes
Ottawa
TorontoEh wrote: Pete, I've heard about running it constantly and all-day fan but do you think apart from the hydro bill, there are any other consequences? The fan/motor will have to work harder if its not stopped for a period of time. Right now, mine comes on during each heating event and I have a schedule setup in my Nest app to run it frequently throughout the day.

I do notice the temp of the home does go up .5 to 1 full degree if fan is on and circulating for a couple of hours but then I always worry about if if my fan motor blows or other components fail?

I don't even know if I have a Hi Eff furnace and if/or it's 1 or 2 Stage like they say now a days. I do use a 3m high merv rating filter (we had some construction done in basement recently) so I was told to use this to capture all dust/particles etc.
I have had my furnace fan running constantly for over 10 years. There is constant air circulation in my house. The air circulation is distributing the air in throughout the entire house whether the furnace is in heat or A/C mode or off.
I do really believe that the house is far better temperature and comfort because of that.
“Those people who think they know everything are a great annoyance to those of us who do.”
Deal Fanatic
Mar 21, 2002
6826 posts
1482 upvotes
Manitoba
Never found any use for mastic. I strictly use foil tape. As has been touched on the cheaper tapes are harder to separate from the paper backing and the foil itself may be slightly thinner than the better tapes. The purpose of the foil is simply to prevent air leakage at duct joints. Beyond that I don't see insulating the ducts as being worth the effort nor cost effective for that matter.

Foil tape incidentally can be bought at places like Home Depot or online at Amazon. Both seem to carry several brands at different quality levels (in HD's case I found different brands in different parts of the store).
Deal Guru
Feb 9, 2006
13377 posts
8308 upvotes
Brampton
woof wrote: Never found any use for mastic. I strictly use foil tape. As has been touched on the cheaper tapes are harder to separate from the paper backing and the foil itself may be slightly thinner than the better tapes. The purpose of the foil is simply to prevent air leakage at duct joints. Beyond that I don't see insulating the ducts as being worth the effort nor cost effective for that matter.

Foil tape incidentally can be bought at places like Home Depot or online at Amazon. Both seem to carry several brands at different quality levels (in HD's case I found different brands in different parts of the store).
People never mention that half the battle of using mastic or tape is just making sure the surfaces you're sealing are cleaned and prepped so it'll stick.

Top