Adding Heat & AC to Basement during Remodel

6 years ago

We are remodeling our basement to add a bathroom/laundry room. The finished area will also have a storage room and living space (total finished area will be approx 1000 sq ft. The entire basement is below grade level.

Right now, all the walls are down to framing so we thought it would be a good idea to add heating and A/C, neither of which existing in the space before. While everything is ripped out, we will be adding insulation and installing sheet rock walls (previously it was 70s wood paneling)

We have received a quote ranging from $10k - $13k to complete this project (we live up in CT)

The quote includes the following equipment:

First Co 24HBXB-HTXV-410A Air handler 13/14 SEER (unit w ducts will measure about 20"D x 70"W)

1 Lennox 13ACX024 410A A/C unit

1 Condensing unit pad

1 50ft refrigeration line (3/4" X 3/8" X 50')

1 Condensate pump

1 Honeywell pro 3000 digital T-stat

Anyone who has installed use these brands? Or would recommend different brands? Does pricing sound about right? Any way to conceal the First Co unit as it will be sitting on floor of work room which is just off of finished basement area? What can we expect as far as noise level? There is a sitting room on main level above the work room.

The rest of the house is heated/cooled by baseboard heat(oil furnace) and central A/C. As with most below grade basements, the area feels cool in summer but humid (used portable dehumidifier to remove moisture) and cold in winter. We have cylinder block foundation so we had contractor use apply Drylok to walls before adding framing. Only had water in basement once due to pool drainage but don't want to risk possible future water damage once basement is redone. Contractor plans on using foam insulation...not sure if this will make much of a difference to current seasonal temps.

Thanks!

Featured Answer

mike_home

6 years ago

Your contractor is proposing installing 2 tons of cooling in an underground basement which has high humidity. He obviously did not do a load calculation. You will spend a lot of money on equipment that will short cycle and still have a humid basement.

I suggest you tap into the current AC duct work and add two or three registers and a return. The cooling load is low, you will probably find yourself closing one or more registers. The return will lower the humidity, but you may still need to run the dehumidifier in July and August.

I think adding foam insulation to basement walls is a little overkill in my opinion. There are less expensive insulation solutions that would work for a finished basement.

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Comments (11)

tigerdunes
6 years ago
How do you plan to heat? Heat strip maybe? Keep in mind BTUs required for below grade basement both heating and cooling will be very low. You have been quoted some low end Lennox junk. I would not have it. Get another quote!

IMO
mharon
6 years ago
The system will be hooked into our existing boiler by adding another zone. Thanks for feedback on Lennox!
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PRO
Austin Air Companie
6 years ago
1000 sq ft is small space. It's a basement so temperature extremes will be minor in relation to a typical structure. You're located in CT and so if there was extreme it would be in winter.

Basements are known as mold havens. The risk for mold growth is very high. Mostly this stems from moisture content and then all you need is a nutrient rich dark place and you are off to the races. (a closet with sheet rock as an example).

For those reasons it is probably best if you use a dehumidifier for cooling control of this area. For heating you could probably just turn the dehumidifier off.

Another option due to size of this area would be inverter mini split as they come in small sizes and run as load matching system. 2 tons of AC is too much for your structure.
mharon
6 years ago
Mike_home and Austin Air-

Thank you for feedback on ton of AC. We are looking to get a second opinion/estimate.

I wish we could tap into existing AC system but blowers are in the attic 3 levels up.
mike_home
6 years ago
What is the temperature and humidity level in the basement during the summer? If it is 75 degrees and over 60% humidity then you don't need any cooling. I would just invest is a good dehumidifier. You will be very comfortable if you can get the humidity down to 40%.

You can invest in a Sante Fe dehumidifer or something similar and not something you buy at a big box store. Perhaps install it in the unfinished part of the basement and have a connect with the finished part with duct work. Add a condensate pump to drain the water outside or into a sump and you won't have to worry about it other than an occasional filter cleaning.
Norah Mahon
Original Author
6 years ago
mike_home - We typically keep the temp on main living levels at 70 year round (both heat & A/C). I haven't checked to see what temp is in basement but it is always noticeably cooler (15-20 degrees?) During summer months we had a portable dehumidifier set to 55 and would have to empty 2-3 times a week during peak summer season. I have a small temp/humidity reader and will put down there today to see what reading I get. Thanks!
mike_home
6 years ago
If it is below 70 degrees in the basement, then there is not need to spend money on installing a 2 ton AC system. The humidity setting on a portable dehumidifier are notoriously inaccurate. Buy yourself a temperature and humidity gauge on Amazon and watch the readings. You need good dehumidifier set up and not more cooling.
Bruce in Northern Virginia
6 years ago
When we finished our basement we put 1" closed cell foam panels on all the walls, taped at seams and sealed at the top and bottom. We then put 2x4 framing inside the foam layer, and added batts of rock wool insulation. Then we sheetrocked the walls and ceiling.

We have found that we do not need A/C (humidity is moderate), and heat can be taken care of by a small portable heater on really cold days. Without the heater, the basement is about 5 degrees cooler than the rest of the house.

I had pre-plumbed for an additional radiator in the basement (we have a boiler and cast iron radiators in the rest of the house), and if I size it properly I think one will be enough to keep it very comfortable. In the basement bathroom we installed an electric heat grid in the floor under the tile, and then have a Panasonic heat/vent unit in the ceiling.

Bruce
ionized_gw
6 years ago
Please, be very careful about the insulation and vapor barrier placement and type. If you don't get it right, you will have a mold farm. I don' t know the situation details, but this could be very easy to mess up. The most important part of the basement to insulate is between the soil line and the floor of the ground level, the rim joist, and environs. I wish I could be enthusiastic about about the Dryloc paint. If you have water outside the foundation, the only good fix is to lower the water level via better drainage. This usually involves a lot of digging. If it is a soil moisture (vapor) problem OK, but get the vapor barrier/insulation right.

Given the oil-powered baseboard, I'll assume that you are in the Northeast. My experience with finished basements in the NE is that when a dehumidifier is running in the summer, you have enough waste heat so that you need little cooling, but two tons, that should be OK for 5000 square feet or more. Oh wait, you have 1000.

Keep the humidity below 50%. An efficient dehumidifier would probably be a good investment, but I don't know about the return on investment. As Mike suggested, you can stick a portable unit into a purpose-built plenum located in an unfinished area and run ducts using a small blower and external thermostat for a pretty effective system (see below). I am assuming that the whole basement is half again bigger or twice the size of your 1000 sq ft finished area. If that is the case and you empty even a largish portable dehumidifier 2 or 3 times a week, that is not a lot compared to some other situations. I've seen 70 pint units fill up daily or in part of a day. Add the pump for when you are out of town and it will be so quiet that you will forget it is there.

Don't (fully) add cooling until you prove that you need it. It if has been cool while running the dehumidifier and the humidity is an an acceptable level, have a plan and and leave an option in place for cooling now, but you don' need to fully execute it yet if it is going to cost a lot in equipment. There are too many unknown (to us and to you) variables in your plan right now that are going to affect your heat and cooling loads. Insulation will be a two-edged sword. Soil temp is probably in the 50s staring a few inches below the surface. Add insulation and you need heat less in the winter, sure, but you lose a heat sink in the summer that might make you need more cooling. If a typical, inexpensive dehumidifier makes it too warm a Santa Fe or similar will make less waste heat and might be tried before adding cooling. Note that a good engineer might be able to model all this for you and get it correct right out of the gate.

A mini split is probably a good option but if you can piggyback on your existing cooling system, so much the better. You might have to install all the ducts, of course and might will be the main investment if tapping into your existing system. On the other hand, maybe a mini split can pretty much be added later with no investment now. As lagniappe, it may provide heat for less cost than the oil burner. Do the math. If you want to use it for heat, location nearer the floor will work better so consider a floor console or setting up a ducted unit with high and low supplies/returns that you switch off seasonally rather than the typical high mount version. They are not as efficient and cost more, but may work a lot better. My experience in finished basements in heating climates is that the floor and feet are always cold. The mini splits in dehumidification mode can take a lot of the load off of a dehumidifier while giving you some cooling at the same time. Make no mistake, however, they are not dehumidifiers. They are always net cooling whereas dedicated dehumidifiers heat as a byproduct.

To see some examples of a dehumidifier in a plenum, find these articles, You can probably forget about most of the other stuff found there unless just for interest. Note that this organization might be a good place to look to check or form your insulation plans:

Conditioning Air in the

Humid South—Creating

Comfort and Controlling

Cost

Research Report - 0214

November-2002

Building Science Corporation

Residential

Dehumidification Systems

Research for Hot-Humid

Climates

Building America Report - 0505

Feb-2005

Armin Rudd, Joseph Lstiburek, P.Eng., and Kohta Ueno
mharon
6 years ago
Thank you for all the info and feedback. I managed to talk my DH into getting a second opinion on what we may or may not need for proper heating/cooling and dehumidifier options. I did put a thermometer/humidity reader in the space last night so i can track both readings for a few days.

Adding Heat & AC to Basement during Remodel

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Adding Heat & AC to Basement during Remodel

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