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Ask me anything about HVAC heating air conditioning air quality control

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Newbie
Jun 21, 2007
52 posts
2 upvotes
Hi Brian,

I'm finishing my basement this spring and want to seal my ductwork joints as they are really leaky.

Most ducts are running in the floor joist cavities and space is limited. I've taped as many areas as the space allows but still have many leaky areas. I was thinking of using mastic to seal the joints before I drywall as I could get a paint brush in to some of the tighter areas. Do you have any thoughts and were can I buy the stuff. The big box stores don't sell it.

Thanks for your help.

Scott.
Deal Addict
Dec 27, 2007
1074 posts
164 upvotes
Markham
foam wrote: Hi Brian,

I'm finishing my basement this spring and want to seal my ductwork joints as they are really leaky.

Most ducts are running in the floor joist cavities and space is limited. I've taped as many areas as the space allows but still have many leaky areas. I was thinking of using mastic to seal the joints before I drywall as I could get a paint brush in to some of the tighter areas. Do you have any thoughts and were can I buy the stuff. The big box stores don't sell it.

Thanks for your help.

Scott.
There is a place in Richmond hill on leslie and 16th ave called Trent Metals. They sell that stuff there.

Now before you go throwing this stuff on, you should look at getting someone to make sure the duct is all put together properly. Most of the guys who do "new home" construction are paid by the house, so they want to get in and out asap. This leads to large gaps. What should happen is the duct shouldn't need any tape or sealant to be sealed.

I would take a look at that first before coating.
Newbie
Jun 21, 2007
52 posts
2 upvotes
bririp wrote: There is a place in Richmond hill on leslie and 16th ave called Trent Metals. They sell that stuff there.

Now before you go throwing this stuff on, you should look at getting someone to make sure the duct is all put together properly. Most of the guys who do "new home" construction are paid by the house, so they want to get in and out asap. This leads to large gaps. What should happen is the duct shouldn't need any tape or sealant to be sealed.

I would take a look at that first before coating.
Thats great, I travel up to that area on business quite a bit.

I did have a local contractor in to look at moving some ductwork for me (he can't) and did say the work was sloppy, and mastic would be a good solution.

You've been around the block so to speak, I didn't mention that I live in a new house (6 years old). It's a shame that the quality of workmanship has dropped off so much with new home construction.
Newbie
Oct 3, 2007
29 posts
3 upvotes
mississauga
Hi, I have a question about insulating ducting.

I have a 35 year old house with what I believe is original ducting. For the main duct (16"x8") do you believe that there is any value in wraping it with insulation? Or would there be more value in just using a product to seal the joints?

Cheers
Deal Addict
Dec 27, 2007
1074 posts
164 upvotes
Markham
Insulating is a very hard thing to do...it is messy and hard work to do it neatly. It is also quite expensive.

However it is well worth the time and investment!
Newbie
Oct 3, 2007
29 posts
3 upvotes
mississauga
I'm doing a room in my basement and a good chunk of the main duct goes through it, so I'm wrapping that and the branch duct that go through that room since all the walls are down.

The product that I found at Rona is a bubble-wrap that has aluminum on one side. I've put it aluminum-side-in, and I notice a huge difference when touching bare heat-duct verses the wrapped duct. I'm not sure if this is the best product on the market, but it's all that I could find at Rona.

Also, is it worth buying the aluminum duct tape or should I stick with regular duct tape for covering air holes in the ducts?

Cheers
Deal Addict
Dec 27, 2007
1074 posts
164 upvotes
Markham
Definately buy the aluminum product. It sticks and bonds once heated. Regular duct tape will peel off with time. Make sure you also wipe the area that is going to be taped before you tape, dust will cause it to peel later on

cjbenedict wrote: I'm doing a room in my basement and a good chunk of the main duct goes through it, so I'm wrapping that and the branch duct that go through that room since all the walls are down.

The product that I found at Rona is a bubble-wrap that has aluminum on one side. I've put it aluminum-side-in, and I notice a huge difference when touching bare heat-duct verses the wrapped duct. I'm not sure if this is the best product on the market, but it's all that I could find at Rona.

Also, is it worth buying the aluminum duct tape or should I stick with regular duct tape for covering air holes in the ducts?

Cheers
Newbie
Oct 3, 2007
29 posts
3 upvotes
mississauga
Thanks, I'll definitely use the aluminum tape then. I just wish it wasn't so expensive... the guy at Rona told me to use duct tape, I gotta stop listening to them... :D

Do you have an opinion about the aluminum wrap that I'm doing my duct in? If mine is not the best product what should I buy next time?

Cheers
Newbie
Feb 11, 2008
2 posts
1 upvote
Hi Brian,

Do you install Desert Spring furnace humidifier? If so, what's your rate? You can send me a private message. Thanks.
Deal Addict
User avatar
Feb 24, 2005
1247 posts
93 upvotes
Toronto
buyways wrote: I have a gas-heated hot water radiator system (90-year old house) with a couple of issues...One is that there is water coming from what seems to be an overflow pipe on the furnace - I'm collecting and dumping about a gallon a day...The second issue is that the downstairs rads get much hotter than the upstairs rads...Third, the house had a kitchen extension built on about 50 years ago and they ran a hot water pipe to a finned radiator... that really throws off very little heat...
pkguy wrote: If you're emptying all that water each and everyday you have backup pressure problems or a stuck water intake valve. When you're not getting heat to the upstairs it usually means their is air in the system stopping the hot water etc etc etc...
nornet wrote: Excellent advise, my only addition would be that the problem is most like with your overflow tank not the rads themselves. The overflow tank must have some water in it but not be full. (100 year old 2 story with asbestos clad pipes).

update: The guy I called in replaced the backflow preventer and the auto-feed (on the pipe providing the water supply from the city to the boiler) after deciding they were plugged from sediment (they were, as I saw once the old ones were removed). He said this should improve pressure in the system and help with the overflow and the no-heat-upstairs and the no-heat -in-the- kitchen-extension problem. The idea was that the lack of flow meant that distant radiators weren't getting hot water and that heat was not being removed from the boiler fast enough, so its overflow/overheat valve was releasing. After he replaced the backflow-preventer and the auto-feed, though, we still weren't getting good heat in the kitchen or upstairs. He then concluded that there was still a lack of good circulation, caused either by a design flaw, i.e. that our pipes were designed for 'gravity' distribution (not pumped distribution) or that diverter thingies that shuttle water from the main line to each radiator were busted. Problem is the pipes are so old he was worried about even opening the main line to check if there are diverter thingies, much less that they are working.

The pipes are currently arranged such that there is a single loop from and back to the boiler, with each radiator having a supply and return pipe from and back to that main line. He says that in the absence of a diverter in the main line between the supply and return branches from the main line to each rad, the water will hardly move through the rad at all, instead mostly flowing through the main pipe in a futile loop. What heat we get is from the hot water slowly rising (like hot air) through each rad; what we should have is hot water pumping through each rad. The kitchen is just too far (and no higher than) the main line. In other words, it looks like our pipes were installed in pre-pump days, and we don't know if the people who installed the pump failed to put in diverters (the sections of the main pipe between each rad suplpy&return look like regular pipe from the outside) or the diverters are (all) broken.

His suggestion is to put in a second 'main line' and re-jig each rad's connections such that one main line supplies all the rads and a second 'main line' collects all the rad returns. (that way, each rad would be connected to two 'main lines' instead of the current one)

here are some schematics - we seem to have a "Monoflow Hydronic Loop" that has either no diverters (as could be the case if it was originally intended to work by gravity and was not properly updated when a pump was added) or broken diverters:

http://highperformancehvac.com/boiler-h ... rangements

The repair guy is suggesting we make it into a "Two Pipe Direct Return Hydronic Loop" or the similar "Two Pipe Reverse Return Hydronic Loop"

Here is my question: wouldn't it be simpler (ie cheaper) to make it into a "One Pipe Series Hydronic Loop"? I.e. could we not just cut and cap the main line's sections between each rad's supply and return, forcing the water to flow through each rad and creating one single house-wide continuous loop from the boiler, through each rad, and back to the boiler? (oh, and I'm assuming that the repair guy would have noticed if this was all caused by a broken pump)
Jr. Member
Jan 16, 2006
152 posts
3 upvotes
Hi Brian,

In my powder room, I got a contractor to install an exhaust fan which obviously exhuasts directly outdoors. The problem I am finding is that on cold days, the room is absolutely freezing and being that the duct is directly below the washroom upstairs and susequently below the bath tub, the tub is freezing too! Is my only option tearing down the ceiling and insulating the duct?

thanks ahead of time.
Deal Addict
Jan 4, 2007
1354 posts
15 upvotes
buyways wrote: update: The guy I called in replaced the backflow preventer and the auto-feed (on the pipe providing the water supply from the city to the boiler) after deciding they were plugged from sediment (they were, as I saw once the old ones were removed). He said this should improve pressure in the system and help with the overflow and the no-heat-upstairs and the no-heat -in-the- kitchen-extension problem. The idea was that the lack of flow meant that distant radiators weren't getting hot water and that heat was not being removed from the boiler fast enough, so its overflow/overheat valve was releasing. After he replaced the backflow-preventer and the auto-feed, though, we still weren't getting good heat in the kitchen or upstairs. He then concluded that there was still a lack of good circulation, caused either by a design flaw, i.e. that our pipes were designed for 'gravity' distribution (not pumped distribution) or that diverter thingies that shuttle water from the main line to each radiator were busted. Problem is the pipes are so old he was worried about even opening the main line to check if there are diverter thingies, much less that they are working.

The pipes are currently arranged such that there is a single loop from and back to the boiler, with each radiator having a supply and return pipe from and back to that main line. He says that in the absence of a diverter in the main line between the supply and return branches from the main line to each rad, the water will hardly move through the rad at all, instead mostly flowing through the main pipe in a futile loop. What heat we get is from the hot water slowly rising (like hot air) through each rad; what we should have is hot water pumping through each rad. The kitchen is just too far (and no higher than) the main line. In other words, it looks like our pipes were installed in pre-pump days, and we don't know if the people who installed the pump failed to put in diverters (the sections of the main pipe between each rad suplpy&return look like regular pipe from the outside) or the diverters are (all) broken.

His suggestion is to put in a second 'main line' and re-jig each rad's connections such that one main line supplies all the rads and a second 'main line' collects all the rad returns. (that way, each rad would be connected to two 'main lines' instead of the current one)

here are some schematics - we seem to have a "Monoflow Hydronic Loop" that has either no diverters (as could be the case if it was originally intended to work by gravity and was not properly updated when a pump was added) or broken diverters:

http://highperformancehvac.com/boiler-h ... rangements

The repair guy is suggesting we make it into a "Two Pipe Direct Return Hydronic Loop" or the similar "Two Pipe Reverse Return Hydronic Loop"

Here is my question: wouldn't it be simpler (ie cheaper) to make it into a "One Pipe Series Hydronic Loop"? I.e. could we not just cut and cap the main line's sections between each rad's supply and return, forcing the water to flow through each rad and creating one single house-wide continuous loop from the boiler, through each rad, and back to the boiler? (oh, and I'm assuming that the repair guy would have noticed if this was all caused by a broken pump)
One of your problems may be the knowledge level of the contractor you called. I wouldn't think there are too many qualified hydronic system experts in Mississauga. I know even in the older part of TO it can be hit or miss. There are a lot of plumbing contractors who install these systems for a living that don't know how they work. Our last system was installed with the expansion tank on the wrong line. Can you get a second opinion? Enbridge has a lot of old timers who know these systems well. Europeans also tend to know them as they are still commonly used there.
Deal Addict
Jan 21, 2003
1141 posts
11 upvotes
Brian,

I am finishing a 300 sq ft space in my basement that currently has 2 supply ducts and 1 fresh air duct in the ceiling. I've heard mixed things, but generally that it's best to bring all of the vents down to the floor. Is this correct, and if so, how close to floor level should I go (ie should I leave a few inches or should it be right down to where the carpet will be?) As well, should I be adding a 2nd cold air return?

Thank you!
Deal Addict
User avatar
Feb 24, 2005
1247 posts
93 upvotes
Toronto
nornet wrote: One of your problems may be the knowledge level of the contractor you called. I wouldn't think there are too many qualified hydronic system experts in Mississauga. I know even in the older part of TO it can be hit or miss. There are a lot of plumbing contractors who install these systems for a living that don't know how they work. Our last system was installed with the expansion tank on the wrong line. Can you get a second opinion? Enbridge has a lot of old timers who know these systems well. Europeans also tend to know them as they are still commonly used there.
that sounds like good advice. he did say he'd never seen a system like this, so that a pretty good clue... :lol:
Deal Addict
User avatar
Jan 13, 2004
3692 posts
273 upvotes
Can you recommend a good text (or a few of them) for someone with basic ventilation knowledge (fan curves, flow rates, volume, pressure, etc.) and access to velometer/anemometer who wants to optimize their home HVAC ducting?
Everything in moderation... including moderation :twisted:
Deal Addict
User avatar
Jul 26, 2004
3356 posts
62 upvotes
Ontario
I have a cold air return coming from the 2nd floor hallway to the basement. Can I add an opening to this on the main level to share the return to the basement. Or do the 1st floor and 2nd floor returns need to be separate?
Deal Addict
Dec 27, 2007
1074 posts
164 upvotes
Markham
If you cut it open on the first floor, you will loose 80%+ of the suction on the second. Your best bet would be to add another one on the 1st floor if you feel that it doesn't have sufficient pull already
dgmorr wrote: I have a cold air return coming from the 2nd floor hallway to the basement. Can I add an opening to this on the main level to share the return to the basement. Or do the 1st floor and 2nd floor returns need to be separate?
Deal Addict
Jan 4, 2007
1354 posts
15 upvotes
Bazooka Joe wrote: Can you recommend a good text (or a few of them) for someone with basic ventilation knowledge (fan curves, flow rates, volume, pressure, etc.) and access to velometer/anemometer who wants to optimize their home HVAC ducting?
Try your local library. If you're in the GTA use the reference either downtown or North York. do an online search http://www.torontopubliclibrary.ca/ Look for books by ASHRAE (American Society of Heating and Air conditioning Engineers).
Newbie
Aug 15, 2007
5 posts
1 upvote
Mississauga
Hello Brian,

I thought I'd take you up on your offer for free advice. Woohoo.

I've got a 20 year old house with it's original gas furnace. A little while ago I had a service call to re-light the pilot and the tech told me that I should seriously consider replacing the furnace. It looks rusted and ready to go. The rust is at the bottom that developed because of a water heater flood I had a few years back. I'm guessing I should replace it now since I eventually have to replace it later, but spending $$$ when I don't have a problem NOW, bugs me slightly. Can you convince me one way or another or just give me questions I should ask myself please?

If I do decide to buckle down, how much should I be looking at? It's a two storey house at about 2,700 square feet.

thanks in advance,
Zohar
Jr. Member
Jan 2, 2008
103 posts
15 upvotes
a1e1a5
Will Heat recovery unit cause my home heating costs to increase?

Dave

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