Utility room is FREAKIN' HOT!

[jonnyGURU]

So yesterday it got cold enough to flurry, so I turned the heat on. After about 15 minutes of the heat being on, I had to run down into the utility room for something.

I opened the door and was hit with a rush of hot air. Of course, there's ducts going every which way in this room and you can't put an arm out without hitting one of them. I touched one and noticed it was EXTREMELY hot and couldn't help but think that this heat is being wasted by being radiated out into a small, uninhabited utility room.

There is some insulation made that can wrap around the ducts to help keep the heat in them until the air reaches the next floor up, right? Or am I being too simplistic?

 

[DisgruntledVirus]

Build a contraption to drip water on the pipes to produce steam, and turn it into a sauna room. Charge the wife and family to enter the room.

 

[Modular]

I know they make something like this (my parents house has it all over the ducting). Sorry, but I have no idea what it's called, just that it exists. Have a Home Depot nearby?

 

[jonnyGURU]

Yeah. I seem to remember some sort of quilted foil looking stuff. Probably glass on the inside. Not sure why a 10 year old house wouldn't already have it's ducts insulated on the outside.

 

[dullard]

Yes, metal ductwork loses heat to the utility room. But so what? As soon as the utility room is warm, your ducts won't lose any signficant heat to that room any more. The room itself is your insulation. And since utility rooms are usually centralized, most heat that escapes the utility room goes right into your house where you want it. It is not really a loss to you.

Sure, you can insulate the ducts. But you won't save anything on your utility bills in most cases.

 

[jonnyGURU]

Originally posted by: dullard
Yes, metal ductwork loses heat to the utility room. But so what? As soon as the utility room is warm, your ducts won't lose any signficant heat to that room any more. The room itself is your insulation. And since utility rooms are usually centralized, most heat that escapes the utility room goes right into your house where you want it. It is not really a loss to you.

Sure, you can insulate the ducts. But you won't save anything on your utility bills in most cases.

I understand what you're saying, but I don't agree with your assessment.

The room would have to heat up to the temperature of the duct before the room became, in itself, insulation. That's pretty hot and the time leading up to that point isn't exactly instantaneous, so I wouldn't say there'd be no savings if I were to somehow insulate the ducts.

Furthermore, the utility room is in the finished basement, and is about 10 x 20 in size. Although the room is centralized, heat escaping from the utility room wouldn't escape into parts of the house that need it (first and second floor)... at least not right away. It would heat the surrounding rooms of the basement which actually stay quite warm year round due to being 6' in the ground and only having an interior entrance way (through the kitchen).

Also, the ducts and the room are much hotter than what the thermostat is set at. Thermostat is on the ground floor. The room will get hotter and hotter until the temperature rises at the thermostat. This is a similar problem to what I have going on at the second floor. The second floor gets very hot. But the ground floor only gets gradually hot. Sure, eventually the heat from the second floor will work it's way down to the ground floor, but by then you're passing out from the heat if you're upstairs and the gas bill is huge because you're trying to heat up the ground floor. Hopefully I've remedied this by closing off half of the vents on the second floor. We'll see.

So, although I agree that the heat would eventually exit out of the room and through out the house, it's still warming a room, a considerable amount, which in turn would have to be costing a lot of money.

 

[Jeff7]

Originally posted by: dullard
Yes, metal ductwork loses heat to the utility room. But so what? As soon as the utility room is warm, your ducts won't lose any signficant heat to that room any more. The room itself is your insulation. And since utility rooms are usually centralized, most heat that escapes the utility room goes right into your house where you want it. It is not really a loss to you.

Sure, you can insulate the ducts. But you won't save anything on your utility bills in most cases.

That's lost energy there, spent heating the utility room. Then with there being a thermal differential between the room and its surroundings, you suddenly have a very large surface area which is held at an elevated temperature, and it's going to want to expel that thermal energy somehow. The question then becomes, how well-insulated are the door, walls, ceiling, and floor of the utility room?

Maybe you can just wrap the ducts in a good layer of fiberglass? I'd hope that some sort of simple product would exist to do this easily though.

 

[jonnyGURU]

Originally posted by: Jeff7

Maybe you can just wrap the ducts in a good layer of fiberglass? I'd hope that some sort of simple product would exist to do this easily though.

Yeah... I saw this stuff: http://www.jmhomeowner.com/pro...egory=ExternalDuctWrap

Looks like I can buy it at Menards. Never been in a Menards because they seem to be the Wal-Mart of home improvement (where Home Depot is the K-Mart and Lowes is the Target), but I might have to go ahead and pay them a visit.

 

[dullard]

Originally posted by: jonnyGURU
So, although I agree that the heat would eventually exit out of the room and through out the house, it's still warming a room, a considerable amount, which in turn would have to be costing a lot of money.

In your case, the vast majority of the money you'd lose is the heat going from the utility room through the basement floor. The ground is about 50°F and the concrete pad is fairly thick and of reasonably low thermal conductivity. Thus, you don't lose too much through basement floors. You'd never see the difference in your utility bill.

Now, theoretically there is a very slight difference in the amount of time that it took for your house to heat up from a cold start. Since the utility room would be sucking up heat from the furnace while the utility room heats up, this is heat that doesn't make it to the rest of your house right away. But I hightly doubt that there is enough difference even there to notice.

Go ahead and insulate the ducts. You won't see the difference on your utility bill. But it'll make you feel better. Duct insulation is not TOO expensive, but it will cost you.

You did describe Menard's well. Menard's generally has the exact same types of items as the other home improvement stores, but you'll get absolutely no service. In exchange, you usually get a slight price reduction at Menards. I shop at Home Depot when I don't know what I'm doing and need assistance, but at Menards when I do know what I am doing and just need the stuff cheap.

<- Dullard, PhD in chemical engineering doing classwork and experimental work mostly in heat transfer.

 

[jonnyGURU]

I trust you do believe what you're saying and you may very well be right. I just can't wrap my head around the fact that a room getting heated that doesn't need to be heated, one floor below the rooms that do need to be heated, isn't making a difference in the heating bills.

I'll have a look at what the duct wrap costs, but not before I take some temperatures of the utility room and the ducts.

 

[Old Hippie]

Get some great big heatsinks and a fan and....................................

 

[sdifox]

So you wash your cloth and hang them dry in the utility room. Just run a couple of cloth lines and you no longer need to tumble dry!

 

[Paperdoc]

I'm thinking in another direction, here, because I have experienced this. Check the dust filter systems on the furnace - they may need cleaning.

On my furnace there is a first-stage dust filter that really is simply some metal frames with something like window screens in it. They trap the very largest particles like lint and hair, but eventually they start to plug up and get blinded with finer particles like "real" dust. They can be removed and cleaned easily with a vacuum cleaner. After them is an electrostatic dust removal system consisting of modules of plates and wires. They can be removed (you must turn off the power switch on the filter unit first) and washed off with water - I do this with a hand shower in the tub - then dried out, replaced and the power switch turned back on.

If my filters get clogged, especially the first-stage screens, the volume of air flow is reduced substantially. Then although the furnace comes on, the lower air flow going through is at much higher temperatures, making all the ducts hotter. Since I'm used to the sequence of operations on my furnace, I know the filters are really bad (and should have been cleaned sooner) when I hear it cycle on and off rapidly because the heat exchanger zone gets too hot (from inadequate air flow) and a high-temp limit switch shuts the furnace down temporarily until it cools.

A last detail. My furnace is a high-efficiency gas unit. The tertiary heat exchanger in it is an array of finned tubes right above the forced-air fan, so they are the first to be cooled by the recirculating air stream. With thier closely-spaced fins they collect a lot of dust over time (the dust filters are not perfect, ever!), so this heat exchanger itself needs yearly cleaning to ensure full air flow through the furnace.

 

[jonnyGURU]

Originally posted by: Paperdoc
I'm thinking in another direction, here, because I have experienced this. Check the dust filter systems on the furnace - they may need cleaning.

On my furnace there is a first-stage dust filter that really is simply some metal frames with something like window screens in it. They trap the very largest particles like lint and hair, but eventually they start to plug up and get blinded with finer particles like "real" dust. They can be removed and cleaned easily with a vacuum cleaner. After them is an electrostatic dust removal system consisting of modules of plates and wires. They can be removed (you must turn off the power switch on the filter unit first) and washed off with water - I do this with a hand shower in the tub - then dried out, replaced and the power switch turned back on.

If my filters get clogged, especially the first-stage screens, the volume of air flow is reduced substantially. Then although the furnace comes on, the lower air flow going through is at much higher temperatures, making all the ducts hotter. Since I'm used to the sequence of operations on my furnace, I know the filters are really bad (and should have been cleaned sooner) when I hear it cycle on and off rapidly because the heat exchanger zone gets too hot (from inadequate air flow) and a high-temp limit switch shuts the furnace down temporarily until it cools.

A last detail. My furnace is a high-efficiency gas unit. The tertiary heat exchanger in it is an array of finned tubes right above the forced-air fan, so they are the first to be cooled by the recirculating air stream. With thier closely-spaced fins they collect a lot of dust over time (the dust filters are not perfect, ever!), so this heat exchanger itself needs yearly cleaning to ensure full air flow through the furnace.

Good thought... and I will check this when I get home. But the rest of the house isn't not getting hot. In fact, the vent in the master bath upstairs gets so hot you can burn yourself when you step on it!

 

[Vette73]

Go to lowes.com and/or homedepot.com and type in " Duct Wrap Insulation "

Yopu will get this " Thermwell Foam and Foil Duct Insulation ". It is a little cheaper at lowes in my area.

That is what you want. It will not trap all the heat but will make it so it does not take as long for the duct work to heat up and pass the heat upstairs. And i disagree with dullard in that it will save money as the rooms you stay in the most will warm up faster and those are the rooms that have the thermostats so the heat will turn off sooner as those rooms get warm faster without really heating up the utility room.

And for furance filters get the cheapest pleated ones. They catch more dirt then the basic ones but don;t block the air flow as much as the more costly ones.

 

[jonnyGURU]

Originally posted by: Marlin1975
It is a little cheaper at lowes in my area.

Doesn't surprise me. Have you ever price compared HD and Lowes? This plywood incident REALLY set me off:

http://www.jongerow.com/blog/p.../11/Outsourced-PLYWOOD!!.aspx

http://www.jongerow.com/blog/post/2008/10/12/Lowes-FTW!.aspx

 

[Vette73]

Originally posted by: jonnyGURU

Originally posted by: Marlin1975
It is a little cheaper at lowes in my area.

Doesn't surprise me. Have you ever price compared HD and Lowes? This plywood incident REALLY set me off:

http://www.jongerow.com/blog/p.../11/Outsourced-PLYWOOD!!.aspx

http://www.jongerow.com/blog/post/2008/10/12/Lowes-FTW!.aspx

Right now the prices at the 2 BORGS is all over the place. The slow down at first lowered the price of lumber/plywood/etc... but then gas went up and so did wood prices. Now with gas coming down and neither one giving a lot of coupons out anymore they are at least trying to match the lumber yards and other discount places at face or better now.

But chinese plywood is not, IMO, as strong or stable as american/canadian made plywood. Esp. the cabinet grade stuff. I do some wood working and have NEVER heard anything good about the chinese stuff.

 

[dullard]

Originally posted by: Marlin1975
And i disagree with dullard in that it will save money as the rooms you stay in the most will warm up faster and those are the rooms that have the thermostats so the heat will turn off sooner as those rooms get warm faster without really heating up the utility room.

Crude math time. I will make some assumptions of course, feel free to attack the assumptions if you feel that they are incorrect. But at least give a good scientific justification as to why you are attacking them.

Assumptions:
1) I assume the hot vents line the utility room ceiling.
2) I assume that the utility room is centralized in the basement. Thus, heat that flows through the utility room ceiling is not wasted heat.
3) I assume that the basement rooms around the utility room are rooms in use or that they at least allow heat to flow from them to the rooms in use above them. Thus heat lost through the utility room walls is not wasted heat. I can see people unhappy with this assumption, but then the best solution is to insulate these interior walls, not the ductwork.
4) I assume that there isn't any strong forced convection in the utility room. That is, I assume there aren't strong drafts within an interior centralized room. If this isn't the case, it probably comes from holes in the ductwork allowing hot air to flow into the utility room and that is your real problem - not insulation. Fix the holes and you are done.
5) I assume no other complications: just concrete below, ducts above, and air in-between.
6) I assume average concrete of 1 W/m/K thermal conductivity and 4" thick.
7) I assume the ducts are 6' above the floor with air of 0.026 W/m/K thermal conductivity between the concrete and the ducts.
8) I assume the "hot enough to burn" means the ducts are at 150°F and that the ground is at 50°F.

Results:
1) With those assumptions, this is a 1-dimensional thermal conductivity problem. We only need to calculate the temperature of the top of the concrete floor. This concrete floor is not the air temperature. Step on it with bare feet, and you'll feel that it is cold.

2) The temperaure of the top of the concrete floor is calculated by:

(Tfloor) = (Tducts - Tground*alpha) / (alpha + 1)

where

alpha = (Kconcrete * Dair) / (Kair * Dconcrete)

Kconcrete = conductivity of concrete = 1 W/m/K
Dair = distance of the air between concrete and ducts = 6 feet
Kair = 0.026 W/m/K
Dconcrete = 1/3 feet
Tducts = temperature of ducts = 150°F
Tground = temperature of ground below concrete = 50°F

Thus, alpha = 692.3 and Tfloor = 50.14°F. Yep, the concrete floor feels cold because it is cold. This is true even if the utility room air feels hot (The air actually would be dangerously hot at the top and gradually becoming cooler towards the floor if these assumptions are true).

3) The heat loss is through the ground and is calculated by:

Ploss = Power lost = Kconcrete * (Tfloor - Tground) * Afloor / Dconcrete

where

Afloor = 200 ft^2.

Thus, Ploss = 14.9 watts. You lose about the same amount of energy as 1/4th of a typical lightbulb because the utility room is hot. Or just a bit more than one CFL bulb.

4) What does this cost you? Where I live, electricity goes as high as 10 cents per kilowatt-hour. If you go by gas heating, it'll be even cheaper.

Cost = 14.9 W * 24 hr * $0.10/KwHr = 3.6 cents per day

Now, you tell me if saving 3.6 cents per day is worth the labor and expense to insulate the ducts. Hint: if it were worth it, it'll be in the building codes. If you really can't stand that massive 3.6 cent loss, throw down an old rug in the utility room (ie insulate where the heat is lost).

 

[Capt Caveman]

Sorry Dullard but some of your assumptions are wrong. Any heat that escapes into any of the adjacent rooms on the bottom floor before moving up to the above floor will become cooler and less efficient than if the OP wrapped the ductwork in the utility room, allowing less heat to escape downstairs.

My first house had no insulation on any of heating pipes from my steam furnace in the basement. The basement was warmer than the rest of the house. After wrapping all of the pipes with insulation, the basement temperature dropped by 10 degrees(lower than the set thermostat temp on the above floor). I can't remember the exact dollar amount but I estimated that I save around 10% on my monthly natural gas bill.

 

[dullard]

Originally posted by: Capt Caveman
Sorry Dullard but some of your assumptions are wrong. Any heat that escapes into any of the adjacent rooms on the bottom floor before moving up to the above floor will become cooler and less efficient than if the OP wrapped the ductwork in the utility room, allowing less heat to escape downstairs.

If you don't use the other basement rooms, then you'll do better by insulating those walls, not the ducts. Wall insulation is far cheaper and easier to install, not to mention it still allows access to the ducts for future repairs.

 

[Capt Caveman]

Originally posted by: dullard

Originally posted by: Capt Caveman
Sorry Dullard but some of your assumptions are wrong. Any heat that escapes into any of the adjacent rooms on the bottom floor before moving up to the above floor will become cooler and less efficient than if the OP wrapped the ductwork in the utility room, allowing less heat to escape downstairs.

If you don't use the other basement rooms, then you'll do better by insulating those walls, not the ducts. Wall insulation is far cheaper and easier to install, not to mention it still allows access to the ducts for future repairs.

You're not a home owner are you? With ducts running along the walls, it'll actually be easier to insulate the ducts. Also, why trap even more heat in the utility room when your goal is to move the heat upstairs? It'll be more efficient to insulate the duct work to reduce the amount of heat loss.

 

[dullard]

Originally posted by: Capt Caveman
You're not a home owner are you? With ducts running along the walls, it'll actually be easier to insulate the ducts. Also, why trap even more heat in the utility room when your goal is to move the heat upstairs? It'll be more efficient to insulate the duct work to reduce the amount of heat loss.

You have no idea what you are talking about do you?

Yes, I am a homeowner. Who said anything about ducts along walls? None of mine are, nor are any of any homeowner that I've seen with a basement utility room. As soon as the utility room heats up, there really is not any significant additional heat loss (only ~3.6 cents worth per day).

I give you a challege. Properly do the heat transfer calculations for ducts on a wall and I'll let up. Try two conditions: ducts on one wall and ducts on all walls.

 

[Capt Caveman]

Originally posted by: dullard

Originally posted by: Capt Caveman
You're not a home owner are you? With ducts running along the walls, it'll actually be easier to insulate the ducts. Also, why trap even more heat in the utility room when your goal is to move the heat upstairs? It'll be more efficient to insulate the duct work to reduce the amount of heat loss.

You have no idea what you are talking about do you?

Yes, I am a homeowner. Who said anything about ducts along walls? None of mine are, nor are any of any homeowner that I've seen with a basement utility room. As soon as the utility room heats up, there really is not any significant additional heat loss (only ~3.6 cents worth per day).

:laugh: You're the one making a calculation with poorly thought out assumptions.

You assume heat is loss only from the concrete basement floor? Why don't you assume that the type of flooring(hard wood, tile, rug, etc) used on the first floor will affect the amount of heat loss from the heat rising up from the basement due to the lack of insulating his duct work?

Well, I can show you the duct work of my furnace and a number of them run along the walls but thankfully they're insulated. Heck, even the ones that run from the center of the room are insulated. I didn't do it but the heating folks did when I had my new house built. Why would they do something like that?

Now, how about calculating how much warmer the air in the ducts leaving the basement to above will be if the duct work was insulated?

And what holes in the ductwork are you talking about? Why would there be holes? Any duct work should be sealed for efficiency.

edit - the OP hasn't mentioned this but is his basement ceiling insulated or not? This will also affect any heat transfer from the utility room/basement.

 

[jonnyGURU]

Ok ok ok ok... I get dullard's point. And he's not saying the utility room will not heat up before the rest of the house. My issue is that the utility room IS heating up before the rest of the house.

I have a programmable thermostat. The heat is essentially off all day until about 5PM. At 5PM, the heat runs non-stop until the temperature upstairs where the thermostat is hits 68°F. The problem is, this takes longer to accomplish than if I ran the heat throughout the whole day (which would ultimately cost me more, but that's not the point). By the time the rest of the house IS warmed up, the utility room is 100°+. Certainly this time would be reduced IF the utility room did not have to heat up first.

Right?

And no... I didn't get a chance to buy the duct wrap today. Had to replace a bathroom exhaust vent instead.

 

[Jeff7]

Originally posted by: dullard

<- Dullard, PhD in chemical engineering doing classwork and experimental work mostly in heat transfer.

Sounds like I'm outclassed.

<- mechanical engineering student, semi-final semester (next semester is just my senior project)