Basement Very Cold

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Old 03-01-20, 07:37 AM
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Basement Very Cold

Hoping this is the right spot for this and someone can help.
Our house is only about 2000' and of that, the basement has two rooms and a bathroom and is walkout level. Under that is a crawlspace. The basement is running up to 6-7 degrees colder than the main floor. We have had the furnace inspected and all is good and clean. Filters are clean. Furnace tech said ALL vents should be open throughout the house, or air hits the vent and returns to the furnace which is detrimental and damaging to the furnace. We have a two stage gas furnace that is less than ten years old. Anyway, never heard of opening all vents, all the time. Why do we have adjustable vents, anyway? Thinking this is poor info and one reason downstairs is so cold..(hot air rises, as we know). We also just had super thick insulation installed in the crawlspace, which doesn't seem to be helping. I know we could turn on the ceiling fans to blow the hot and cold air around, but I can't help but think the register vents are the best fix. There is a ton of heating duct work running all over the crawlspace and it appears to all be intact. Any other suggestions? Thanks.
 
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Old 03-01-20, 08:35 AM
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Is there a cold air return in the basement?
Is there a hot air register in each of the problem rooms?
I doubt ceiling fans will do much good as you are trying to blow hot air down a level.

I have never heard of hot air turning around and returning to the furnace.
What it can do is build up pressure in the hot air ducting and this in turn can put extra stain on the furnace fan.

In winter I fully open the vents downstairs that I want to heat and partially close some of my upstairs vents.
I also have a cold air return upstairs and downstairs.In winter both are open and in the summer I close off the downstairs cold return so I get most of the air circulation upstairs for the AC. I also close off all the downstairs vents in the summer as the cold AC air just naturally migrates downstairs which is cooler to start with.
 
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Old 03-01-20, 09:17 AM
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Yes, we have a cold air return upstairs and downstairs, and each room downstairs has two registers. Sounds like closing vents upstairs is the best solution in spite of straining the fan...beats freezing or relying on a space heater.
 
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Old 03-01-20, 09:24 AM
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You do not have to close them totally you are just trying to get the right balance.
Listen to the fan with how it is now then do your vents and listen again.
If you hear the fan straining then open up the vents a little more.

You could also partially close off the upstairs cold air return some.
Now it will not only push hot air to the downstairs but increase the pulling the cold air off the downstairs floor.
 
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Old 03-01-20, 04:15 PM
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The only way I can balance my house is to close 3 of 7 vents upstairs in the winter and two of six downstairs in the summer. Previous homes have had similar patterns.
 
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Old 03-01-20, 06:01 PM
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... r air hits the vent and returns to the furnace which is detrimental and damaging to the furnace....
I am sure this is false.

But too many vents closed will put strain on the blower because there are too few square inches of total vent area to support the air flow.

Most furnaces should be able to tolerate a few closed vents.

Are there any places, preferably not too close to the furnace, where additional duct branches including for return air can be added to make up for ducts that get closed. Since you said that the configuration of closed ducts is different for summer versus winter, an extra duct branch or two would be needed both upstairs and downstairs.

See if you can find a small fan that fits over a vent register (and plugs into a nearby wall receptacle) to suck air through and help relieve the strain on the furnace blower.
 
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Old 03-02-20, 02:25 AM
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I am sure this is false.
If closing a vent or two is damaging to the furnace blower, I cant imagine what changing the speed of my multi speed blower motor must do. I've read several posts where people have sworn that closing just a few vents is going to kill the blower & motor.
 
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Old 03-02-20, 04:12 AM
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Let us get the facts straight. Closing off too many discharge vents will not cause a blower motor overload. Reducing the air delivery through the blower will actually cause the blower motor to work less. If you don't believe me get an amprobe (clamp-on amp checker) and see for yourself. Now for the problem, heating a lower level space in the winter will always be a problem since the warm air rises and the cold air falls. To get the temps between the upstairs and downstairs closer you should isolate the 2 floors from each other. Since that is usually not feasible in any normal home the next step is to try to control where the heated air goes. You said that both rooms downstairs have 2 supply registers but you did not mention the location of the downstairs returns. If there is a single return in the basement that may be a problem. (back to this in a moment). If you have 2 supply registers in each room, you should also have 2 return grills, located at or near the floor to remove the coldest air from the rooms. This will not guarantee that the areas will be the same temps but it may be the best that can be accomplished unless the 2 areas are zoned separately to control the temps in each area. Zoning will allow you to precisely control the temps in each area. That would be the best answer but it usually too expensive to do. Now on to a single low level return. It has to be large enough to collect all the air being supplied by all the supply registers in that level and it needs to be mounted near the floor level. If this single return is your case, make sure that you cut the door bottoms enough to allow enough air in each area to escape and flow to the return. I understand that it is not easy to control temps in a home and that most heating systems are not designed the way they should be. One last item, keep the returns open all the time especially in the lower level to constantly remove and recirculate the cold air that accumulates near the lowest floor level. You could also try running the fan constantly in the coldest weather to improve on temps. When you get statements from a tech that makes no sense like "the air will hit the closed vent and return to damage the furnace", show that guy the door" because he has no idea how to fix your problem..
 
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Old 03-02-20, 05:25 AM
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There is one large return floor level on each floor. The filters are there, oddly, not in the furnace. Anyway, never knew you can open and close them. How is this done?
 
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Old 03-02-20, 06:45 AM
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I doubt they are adjustable.
So just covers part of them with cardboard etc.
Be sure that the covering is on the outside of the filters not the furnace side.

Also check the air return duct at the furnace so you have an idea of the square inches.
Again use caution when closing these off as reducing the total air flow too much will be hard on the furnace.
 
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Old 03-02-20, 08:35 AM
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and that most heating systems are not designed the way they should be
And to make it right all a builder needs to do is have a simple 2 or 3 zone system installed for modest cost and these kinds of problems would go away!
 
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Old 03-03-20, 10:52 AM
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I was talking to a builder once about a house remodel the wife and I were going through. We mentioned some of the HVAC changes we were making for the 2nd floor to make it a bit more comfortable. He said that he makes a rule to always advise clients to consider zoning (be it a separate system or zoning dampers). Almost always the customer will decline because they want nice countertops. Fast forward a few months and the customer is upset with both the heating/cooling and the expensive countertops that don't exactly match the appliances.
 
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Old 03-06-20, 05:29 AM
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Return ducts usually do not have controls.

Supply ducts exposed in the basement ceiling might each have a little lever to operate an in-line louver that controls the (heated) air flow.

Register grilles for the supply ducts may have louvers controlled by a knob or lever.

Very rarely is the basement floor insulated enough to prevent considerable heat loss to the ground below. The ground temperature under a house is typically around 50 to 60 degrees year 'round. Concrete is a good conductor of heat so an unfinished basement floor may be considered to be uninsulated.
 
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Old 03-06-20, 08:48 AM
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New R45 insulation installed in the crawlspace ceiling and the basement above is still flipping cold.
 
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Old 03-08-20, 07:18 AM
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Hi Metsker, you're new enough to get another welcome.
I read the entire thread and didn't see a lot about heat loss or air leakage. Fact, if that basement had zero air leakage and was well insulated you would have zero problems as described.

Natural air flow in winter is into the lower areas and up and out upper leaks. That cold air leaking in goes right to the floor so that is why floors are cold. Unless there is water below the slab and around the foundation, the soil 2' below grade becomes an insulator. Your walkout design increases this exposure but is normally handled by lots of insulation.

IMO, your problem is insufficient air sealing and insufficient insulation down there, both of which are probably hidden behind finished walls and ceiling.

I'm a retired energy auditor and always find poorly finished basements to be a challenge because what needs to be done is now difficult and expensive.

I can try to be more optimistic if you share what you know about what is behind those walls.

Bud
 
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Old 03-11-20, 04:32 AM
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I forgot to ask, are the warm air registers and/or the return register at floor level? This would help at least getting the air down near the floor involved in the circulation through the furnace.
 
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Old 03-13-20, 04:27 AM
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Thanks for the welcome!
Yes, registers are at floor level.
Wall next to sliding glass door feels cold so you're probably right about poor insulation in walls.
 
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Old 03-13-20, 04:59 AM
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You can look around the edges of electrical boxes (cover removed) and sometimes see what they used for insulation and also probe beside the box to see how much depth there is. Did they frame wit 2x4's of just apply strapping? Utility areas can also provide a better view.

If you have a drop ceiling you can try to look at the op of the walls and look at the rim cavities for insulation and air sealing?

Bud
 
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Old 03-13-20, 06:02 AM
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It is all about a balancing act and you will never get it perfect without spending a lot of money on making the system dual zone.
Your thermostat is on the upper level so it is regulating the furnace so you need to get as much heat downstairs
as you can while it is on.
So limit the amount of hot air going upstairs by adjusting the registers, This will limit the hot air coming upstairs and force more of it to the open registers downstairs. Also will keep the furnace on longer.
Also blocking all or some of the cold air return upstairs will pull more air over the floor in the downstairs and also help with the air circulation down there.

It will probably take a lot of fiddling to get it right but should be possible to make it comfortable downstairs.

 
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