Basement too cold. Insulating ductwork?

I'm getting ready to install a drop ceiling down in my walkout basement. I should say this will really only be the half of the basement that has finished walls and is set up to be my Home Theater room. In the summer this room is very cold even though I have all the vents and baffles turned off. I'm thinking about insulating the vents to give me some warmth. There is a 15' long square vent running perpendicular and hanging down below the joists and then about ten 6" round ducts branching off this and running tucked up between the joists. Would it be worthwhile insulating these vents to warm up my HT during cooling season? If so, what would be the best way?
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CraigT wrote the following:

My CAC is in the attic. In the winter, after closing the vents, I cover all the plastic AC vent grills with Contac adhesive shelf paper (actually plastic). That keeps the cold air from the attic sneaking past the vent baffles. It may work for you too.
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Bill
In Hamptonburgh, NY
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It's a basement. It's gonna be cooler. Insulating the walls nearest the basement wall would be a reasonable start. After all, those (concrete?) walls are likely to be around 55-60 degrees, and they likely wrap around 3/4 of your anticipated room.
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It would be helpful if you described you house more fully, walkout basement says nothing about what's above it. Also, assumeing forced air heating and cooling, where are air outlts and air inlets????? Maybe you just need to provide a place for the cold air closest to the floor to get into the return ar duct and circulate thru the rest of the house and save some money on air conditioning. MORE INFORMATION PLEASE!!!
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wrote:

It would be helpful if you described you house more fully, walkout basement says nothing about what's above it. Also, assumeing forced air heating and cooling, where are air outlts and air inlets????? Maybe you just need to provide a place for the cold air closest to the floor to get into the return ar duct and circulate thru the rest of the house and save some money on air conditioning. MORE INFORMATION PLEASE!!!
Yes, it is forced air, hence it having ducts. What is above the basement? The living room, kitchen, and dining room.
There are no cold air return registers in the basement. It is my opinion that the bulk of the problem during cooling season is from the cooling ducts leaking and the metal of the ducts cooling the surrounding air.
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CraigT wrote:

I have a hunch that there is an air leak (or more than one) in the ducts that are in the basement, or a duct that is not connected somewhere. Did you check or try feeling for air leaks at all of the duct seams and connections in the ceiling to the upper floor vents and ducts?

Given how cold you describe the basement as being, that seems to be less likely to be the main cause of the problem to me. I have properties with main A/C ducts in the basement and those basements don't get "cold" from those ducts being there.
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wrote:

If the leakage is that bad, it should be fixed. Also, be sure the door to the basement is closed and a lot of cold air is rushing down the steps if not.
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On 6/11/2011 4:06 PM, Ed Pawlowski wrote:

underground. And it is cold in the summer, and in the winter too for that matter. The ceiling is fully insulated. Originally there were no registers in the basement. There are not leaks as it is new construction using flex line and the fiberglass board for distribution boxes. Yes there can be leaks in that type of construction, but I haven't seen any. Actually, I put a register in each of the 3 unfinished rooms just to keep the air circulating, plus one small return. Without some air movement, the air tends to get stale feeling. Being mostly underground is probably what makes it cold. I am going to have a zone installed for one of the 3 rooms, my work room, as I already have a zoned system. It will not be used for AC ... just for heat in the winter. In the summer it is usually about 66 or 67 early in the day. If I am working there, and turn on the dehumidifier, it will warm up to maybe 70. The humidity is only slightly high, so I don't usually run it for long periods. In the winter, I've seen it be as low as 58 and that's with the 3 registers putting in some heat.
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This is usually how I keep my house, open door. Closing it would help. My basement is cool anyway without air. It will be impossible to get it exactly right. The basement needs circulation, may more so the house equalizes. I also in the process of basement renovation. I started out insulating the floor before doing anything else. 5/8 foam over 5/8 plywood.
Greg
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I have yet been able to get zero pressure differential on that basement door. It wants to suck air from the upstairs. Meaning there is too much duct return, and nothing is taped on the rectangular sections which I will correct.
Greg
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Sorry, plywood over marine foam.
Greg
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It probably isn't the cooling ducts leaking, but cool air sinking from the AC upstairs added ti the cool walls. Put in some return air ducts close to floor level to put that cool air into the overall system and save big $$ on air-conditioning costs. Put some supply side registers also in the basement, with flappers or dampers or some means of closing them in the summer, but allowing hot air into the basement in the winter. This is elementary air-handling stuff.. If the ducts were really leaking, you would have too much heat in the winter, and you seem to be saying that the basement level is cold even when the heat is on.
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Sounds like your basement doesnt have any HVAC going to it. Installing/ opening some vents so the air there can circulate with the rest of the house would help IF opening the vents dont help you may not have a path for the air to get back to the return. Try keeping your basement door open and see if it helps.If the cooling is coming from the ground your are misssing out on some energy savings by not using this to assist your HVAC, When I lived in a house with a basement it was much easier to heat and cool than the the one I have now.
Jimmie
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Since the basement is already TOO cold, I don't see how adding HVAC vents is going to help raise the temperature. It will do just the opposite.
Also, I agree with the posters who have said they don't think adding the insulation will make much of a difference. If he has room for it, adding it will help save some energy, but I doubt it will make a noticeable difference in the basement being cold. Most of that cold is coming from the walls and floor and insulating those would bring the most benefit.
Try keeping your basement

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wrote:

I said to add return air registers close to the floor to suck up the cold air and put it into the system to help cool the rest of the house. Supply side registers were to be adjustable, closed so no cold air in the summer going into the room, but opened in winter to help heat the room
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wrote:

I was replying to Jimmies post, not yours and it appears he was advocating adding supply vents. I also think it would be a bad idea to add return registers with no supply registers if the basement also contains any fuel burning eqpt, eg furnace, water heater, etc. By doing so, you'd increase the negative pressure, something you typically do not want to do.
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wrote:

Sorry - I agree with you, supply side and return both advisable. I actually have run a 10" diameter hose from outside of the house to the area of my furnace where the combustion air is normally drawn in top make sure I always have non-heated/cooled air for combustion. Basement always cool even in mis-summer, and warm enough in winter when I open the air registers to get hot air to heat it up. The OP is fixated on leaks which would have to be pretty horrendous to do what he is complaining about
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If the air comming out of the supply registers is warmer than the basement air, it will warm it up. Even if the heat pump is set for cooling. Probabaly not an efficent way of doing it, but that will be the results.
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CraigT wrote:

Are the walls cold (about 50-60 degrees)? If so, you're a recipient of normal earth temperature. In other words, it's not your AC that's cooling the walls, it's the walls cooling everything else.
The only effective way to warm things up is to first insulate the heck out of the basement walls.
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On Sat, 11 Jun 2011 09:54:42 -0400, CraigT wrote:

They install insulted crawlspace ceiling ducts for houses on pads. But this is to keep the air inside the ducting warmer in winter. Keep your air off for 24 hours and measure the basement ambient temp. This way you can decide for yourself if insulating the ductwork will help you. I doubt it will but only this simple test will tell you yes or no.
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