HVAC for your basement. Let's tame this wild beast.
First things first. What the heck does HVAC stand for? The exact definition is Heating, Ventilation and Air Conditioning. I did list HVAC as one of my 8 phases of how to finish a basement but what you're probably wondering is:
- Will it be to hot in my basement in the summer?
- Will it be to cold in winter?
- Will the air in my finished basement smell and feel fresh and clean.
- Will Zack and Kelly eventually get married.
Ok, that last one I just threw in for fun, if you get that reference then you're old and dorky like me awesome.
What do you need to do to your HVAC before you finish your basement?
- Do I need to expand my HVAC?
- Do I need to run new ducts?
- Can I just throw in some new registers?
- How do I make sure my system will be balanced once I add my basement
- Does my furnace have a large enough "capacity" to "service" my basement.
Don't freak out me now. I know there are a lot of questions. Let'scool down for minute. Take a deep breath. Get into your best Yoga pose and consider the following:
- You may not need any HVAC changes. Yup. I didn't change a single thing and my basement is money comfortable.
- You may just need a solution for heating. Especially if you live in a cold-ass state like Michigan, New York or Canada (an awesome Country, not a state, I know).
- In most cases you can add a solution AFTER your basement is finished. So if your budget it tight - you might be just fine waiting a bit. (this is what I did)
In this section on HVAC, I'm going to outline, in a simple and fun way, 163 hours worth of boring grueling research, Google searching, Youtube video watching, and general calling up of HVAC guys asking them questions about HVAC for your basement.
Yes, you're welcome.
Let's start by answering this question...
Will You Need to "Expand" Your Basement HVAC
If the air in your finished basement will be either to hot, too cold or too stale then you will want to either expand your HVAC or add a separate unit (more on why I recommend adding a separate solution a bit later).
So how do we find that out.
Measure Your Basement's Comfort Levels
One of the simplest ways is to buy a thermometer with a humidity reader and put it down in your basement. Maybe even buy two - one for your living space and one for the storage area or the space that won't have any access to windows.
Put a temperature and humidity monitor down in your basement. Make sure it has a 24 hour Low - High functionality.
I highly recommend this little baby here. You can buy it here on Amazon for around $10 bucks, it's a best seller and has 4 stars. Plus, I've personally owned two of them for over a year and they've been fantastic.
Regardless of which brand / model you decide to buy, make sure is has a daily Low / High hold function. You don't want to just sit down in your basement like a creepy serial killer just staring at the thermometer all day.
Ok. So now we're measuring temperature and humidity. What are we looking for?
For me…. I wanted to make sure the high temps stayed below 74 degrees and the low temps above 65 degrees. And humidity between 30% and 40%
Now wait just one second. If you're thinking "65 is way to cold for me" or "74 degrees, holy Christmas, I'll bake in those temps". Hear me out.
Those are the "extremes". On average I'd like to be at 69 or 70. And guess what - with almost not additional HVAC work that's where my basement temps are about 95% of the time.
What's that? You don't have time to wait 12 months to measure your basement temps - keep reading - I have a few samples below.
Consistent, Comfortable Temperatures - Thanks Mother Earth, Your Rock
Here's what's kind of awesome. The earth (the dirt part of it anyway) has a very regular temperature of about 65 degrees, once you get past the first foot or so going down.
I made this uber-professional graphic to try and explain why your basement temps will be fairly consistent year round. Note where the "ground" begins - the "coldness" cannot penetrate the basement as well. Same concept for hot air.
This is why you'll often see insulation only on the top half of the wall of a basement. Because the bottom half of the wall doesn't need it. The ground temps that far down are a constant 65-68 degrees.
3 Factors that can dictate if YOUR basement will be comfortable?
1. What Style of Basement Do You Have?
Is your basement mostly below ground? If it is, you're in luck! The temps will be fairly comfortable and consistent.
My basement is a walk-UP. I have a double door exit to the outside then you have to immediately "walk up" stairs. What this really means is - only the door part of that wall is exposed to the hot sun and cold air.
If your basement doesn't have any exits you're in even better shape (in terms of temp control, in other ways that kinda sucks for you).
If your basement is walk - OUT, then guess what, sad face for you. You might need to spend some extra coin to heat and cool it. The reason is that you likely have an entire wall exposed to the elements.
2. Where Do You Live?
You need to take into account where you live. Me, I live in Virginia, which has a moderate year round climate. Sure, we have our moments of extreme heat or extreme cold but by-in-large we're the Baby Bear of temps - not too hot, not too cold.
Remember, I have a total of 2 registers in my basement... During the coldest week last winter - where temps were in the mid-20's with a foot of snow on the ground - my trusty Acurite Monitor read 63 degrees.
During the hottest week this past summer - the average highs reach 95 everyday for 4 days - the max temp reached 74 degrees, and that was in the room exposed to the double doors.
So not too bad. I was able to get my video game room up to 67 degrees with a $50 plug-in heater. I did not need to add A/C, the 74 was mostly in the afternoon - in the evenings it dropped back down to 70-71.
To all my peeps in Green Bay Wisconsin - you may need to supplement your basement with a heat boost.
To all my peeps in South Georgia - you may need to add an AC boost.
I have a separate article coming soon that lays out your options, my recommendations and what it might cost.
3. How are You Going to Use Your Basement - Just Kickin' it or Living In It?
Finally, what you plan to do in your basement may affect your decision on whether or not spend the extra money to get your temps perfect and controllable year round.
If you're just gonna play some video games or watch movies or host a poker night or two then you're probably good to go with less precise control over the temps.
But if someone is going to be down there a lot, like living there, or you're going to use it as an office (that you actually work in) then you might want to make sure you have control of the temps.
Alright, hopefully that will get you started. If you think you'll just need a bit of extra heat (like me), read my recommendations on heating your basement here.
Do you have a specific question or comment on basement HVAC? Leave it in the comments below - I answer ALL questions.
Cheers - Jason
Other Hot and Cold Links:
I live in Indiana and am currently finishing my basement. It will be about 800 - 850 sq ft and stays a pretty comfortable temp year round and that is without insulation, just the poured concrete walls. Do I have to run HVAC ducts? Do I have to have cold air returns? It will mainly be a play area in the main open part and there will be another room for a home theater. My main concern is moisture control and not temps. Can I get away with only have a dehumidifier in the basement? Thanks!
Adam
Here in Wisconsin it looks like code requires heat vents in every "habitable room." Is that not the case where you are, or did you get around that somehow?
We are finishing the walkout half of our basement and one that side there is only one vent, in what will be the bedroom. The basement stays pretty comfortable and I don't think we really need to add vents or ductwork, but it seems like it is required. Am I wrong?
Hi Katie - Yes, that does appear to be the case for Wisconsin. As with a lot of building codes it can vary. However, it maybe pretty easy to fix - my basement is basically one big open room, one bathroom and one office - so one vent meets the requirements for the open room. The bathroom requires a powered vent so that takes care of that one. Then it's just my office that needs a vent - which wouldn't be hard to put in and shouldn't affect performance (since it's just one).
Give you local building department a call and ask how it's usually handled in your area.
Jason
I finished my basement a while ago and kept all of my HVAC as-is. 3 heat vents in the ceiling and that's it. It came out great and is usually very comfortable, but sometimes in the Winter it gets extremely warm when I am down there for a long time. All of my heat vents are closed in the winter, but I do not have a cold air return. Do you think installing a cold air return would help keep it cool, just to encourage air circulation? I live in a suburb of Cleveland, OH so it is a cold climate in the winter. I appreciate any help you can provide. Thank you!
Hmmmm.... Hi Neal, so that's a new one. You're saying it gets too warm?? In the winter?? In Cleveland?? With the vents closed??? Am I reading that right? Not sure I have a good answer for you on this one. - Jason
We are finishing our basement and have available duct work for adding heat. What is a ballpark figure for adding ducts to an area approximately 42' x 20'? We are not zoning this area, only adding to upper level heat system. Thank you!
Hi Mary - It sounds like you're just asking if how much to tap into an existing trunk line of the HVAC and install a few registers. If that's correct, I would estimate about 2 registers at $20 a piece plus some sheet metal to construct a connector to the trunk - so maybe $50. This article can help you with installing registers. Good luck! - Jason
I have a finished basement with a drop ceiling. What I have noticed is water spots in locations of the upstairs floor vents. I believe the duct work is sweating but when I remove ceiling tiles in locations of the water marks is appears well insulated and nothing is noticeable. Every summer it seems to be a different location / different water mark / stain but only in the locations directly below the floor registers. Suggestions? By the time I notice the spot its dry and time to replace the ceiling tile.
Hi Dan - My suspicion, and this is a just a guess as my knowledge of moisture issues is limited, is that you have too much moisture in the air of your basement. You should use a dehumidifier to keep it at or below 40% humidity. The basement air with moisture is reaching the cooler air in your ducts (cooler I'm guessing because your AC is on in the summer) and the lower temp air can no longer hold that moisture. It then "condenses" on whatever surface is around and drops to your ceiling tile. - Jason
ps. This little humidity monitor by Accurite on Amazon works great!
What are your thoughts on air circulation? If your basement only has 3 vents and no return ducts then how are you circulating in fresh air or air that has been run through your furnace filter?
Hey Brian - I think (I'm not a professional HVAC guy) that the HVAC itself acts as a return, which is why you need to have slatted doors if you enclose your HVAC area. It needs to be able to pull in air. - Jason
My unfinished basement is a 2,000 sq ft walk-out. It is pretty comfortable all year but does smell a little musty. What is the most "economical" heating/cooling/circulation option?
Eric, I'm not sure where you live but it sounds like the musty smell is humidity in the living space in your basement. I have solved similar problems with a dehumidifier but don't go cheap here get one sized for the 2000 sq ft of basement and plumb it into a drain. Good luck.
Hello jerry, we want to finish our basement. we also want to update u and replace our current central air and heating
Do you recommend we change our heating and air unit before or is ok to wait until after. We cant afford
Thanks
I'm sorry typing from a phone..we cannot afford to finish the basement and change the air and heating unit at once.
Hi I am working on me basement and have 2 runs for heat/ac and need to install a return, I was wondering if you could expand on where/how to install a return in the basement or if you already have an article or a link that expands on this topic? Thanks very much in advance
Sorry David - I don't have enough HVAC knowledge to answer that for you. - Jason
My husband and I are going to live in a huge finished basement in my daughters home. He is allergic to their animals. It has a brand new HVAC. My question is , will he still have allergies with a brand new HVAC? Will the pet dander come through vents?
Hi Lori - Well... yes and no. There's no way to completely filter all pet dander but their is quite a bit you can do to mitigate most of it. 1. Use a filter in the HVAC that's design to cat pet dander. 2. Buy a stand alone air filter to clean the air in the basement ( I would recommend doing this anyway, if you're living in a basement, even if you weren't allergic to pets.) Good luck! Enjoy the basement, let us know if he's able to avoid any symptoms. - Jason
Have an Electronic Air Cleaner installed. It will replace the existing filter located at the furnace. This can get expensive (around $1000 or so) but the results are amazing for people with allergies or breathing problems.
Hi Jason,
Thanks for maintaining wonderful website and ideas for basement.
I am building a new house with a local builder in Richmond, VA. The house is a 3 level unit and 2 zone system. I am finishing the basement (walk out style) with the builder , and there is HVAC in attic for 2nd floor, and another is placed in basement which is for both 1st floor and basement. The thermostat is in my 1st floor dining area.
The builder said it is a powerful system to run for both levels, and my question is would 1 unit is good ides for both levels ? Would I be looking at higher electric/gas bills ? What would you recommend in my situation? My concern is, we may be unnecessarily wasting to heat/cool the basement if we are upstairs and 1 unit controlling both levels.
1st floor - 1800 sq.ft
2nd floor - 1600 sq.ft (with open in livingroom)
3rd/basement - 1400 sq.ft finished.
Please advise.
I'd like to follow the answer to this post, as I have almost the exact same situation here in Atlanta, GA. I'm about to finish my basement and I'm trying to decide whether or not to add a separate unit or just let the downstairs unit handle the basement.
Hey Jordan - Even though your down in Hotlanta, I would try tying into the existing unit first. There are a lot of good options of both heating and cooling solutions you could install after the fact that may make more sense anyhow. -Jason
Hello. I live in CT. The basement in the home i live in was already redone and “finished” prior to me and my children moving in. Cosmetically speaking, the finished area LOOKED well done. We built two bedrooms within the finished area and that is now where my older daughters sleep. The past week, it has been cold. -1 degrees today. . The basement - despite having central air ducts and a vent ( i only count one) is very cold. My long-winded question is this: can i cut holes and add more vents to the duct work? Do i resort to space heaters (please say no.) lol what are my options?
I live in Colorado and our basement is always colder than up stairs . We have a concrete floor and nice water proof expensive tile with a thin layer of padding. I think I’m going to have an HVAC expert check it out. I would like to have a small separate system just for basement for main area . What would you suggest?
Could you please talk a bit about the options available for adding A/C after a build-out? We’re having a professional contractor finish our 1,200 sq ft basement in Atlanta into an apartment for parents. Big closet, nice barhrooom, large bedroom, and a very large great room that also has a full kitchen. For heat, we’re going with a ventless fireplace (with thermostat). For cooling, we’re tapping into 1st floor A/C (which does a great job of keeping 1st floor cool). But, what happens if, after finishing, we find out that existing A/C isn’t adequate? Window units are not permitted by HOA. Thanks.
If you are considering finishing your basement and a permit will be pulled for any of the work (electrical, plumbing, ect), call your local inspections dept. and ask if zoning your hvac system is required. If a inspector is there for 1 thing he's going to see Everything and not being educated may come to bite you!
Also, if you think that tapping into your duct system After you've done extensive work only to find that it's not adequit and now you have to add more ductwork - and framing, sheetrock, painting... "I thought I just did all that, now there's more?!?!
We just got the basement finished about a month ago by a contractor. Same HVAC system. Legally no issues(got pass from the city inspectors) It's now rented out.
The issue is that the tenent daily cooks very intense food (mustard oil, onions,garlic etc ). The stinking smell now fills my entire home and it's just disgusting. I don't feel like I live in my own home. Whenever they cook(mostly 11pm to 1am) I wake up from sleep with this intense smell and it just keeps lingering all through my home.
Please help. How do we solve this in the most cost effective way? Location wise, we are in Canada.
Please help.
Hey M - That stinks...bahaha. I'd close off this HVAC zone and install a ductless HVAC system for your renter. Here's a link to a highly rated unit.
- Jason
I am in the Piedmont of North Carolina and have a 2200 sq ft walkout basement on a slab. It has all framing, electric, and pre-plumbing in. It is set up for a bedroom, family room, craft room, two utility/storage rooms, and a large work/storage room. I have a duct-able dehumidifier. The only insulation is rolls on the ceiling of the basement between it and the floor above. The floor above has ducts in the ceiling and the furnace is in the attic. I am looking at very slowly finishing it as money and time permits, and in the most cost effective way. It is hot in the summer and cold in the winter right now. I have done the majority of the work so far by myself. Should I install ductwork? Should I use a heatpump? Not sure where I should start or what tools are out there to help me set up or calculate the HVAC system needed.
We are moving elderly mother into lower level which has egress windows but no doors- so mostly below ground. Because of time constraints we have hired a general contractor. After reading your blog I am concerned we are paying way too much to add 3 more registers (we already have 2 in the finished part of the basement) to our existing furnace which is plenty big enough to handle it. To make it as warm as Mother likes it we inquired about adding a damper system and a separate thermostat so everyone will be happy. When finished it will be 1000 sq.ft. but 500 of it is already finished. Any broad, very broad range of cost would be helpful. Also, after reading your blog I question whether we really need damper system or should we just tie into current furnace and call it a day. I appreciate your thoughts.
I live in Atlanta and have a situation similar to comments of Boot Hill in Sept. 2019. Most framing is there, but I will need to add some. I may need to address soundproofing due to nearby train track. There is one small vent and return to existing HVAC for 1600 sq ft basement, which moderates the temperature, but doesn’t always make it comfortable. Seems at a minimum I will need to add ducting before finishing. For better air isolation and control, I am thinking a small heat pump would do the trick. Does your book address duct installation, and HVAC contractor selection?
Mostly finished bm, half turned into apt by flipping furnace room into kitchen. But yikes just rented before finale touches: it's cold! Cut a heater vent in ductwork that close to furnace?? Ideas for ceiling in furnace & ductwork to provide aesthetics, soundproofing, temp insulation.
Thx
Will 2 registers affect my Hvac unit in my basement
I’m finishing my walkout basement and have 90% of the framing done. I’m trying to decide how much ductwork I need for my walkout basement. My wife will be using it as an office and play room for my kids. The office section will be on the walkout side, and the majority of the playroom will be on the underground side. How many register should I put in, and should I match the duct diameter from the top floor to the basement? (6 inch diameter for the main floor)
We have a finished basement Bd need heat, it’s cold in CT.
We have our furnace already in the basement, have gas heat and radiators on the main floor. We are in a ranch. Our basement does have a wood fireplace but it’s a pan to always have to keep a fire going.
What would be our best approach to having a heat zone in the basement? I’m trying to get cost ideas to see if we can afford it.
Hey, I'm from Alberta Canada, and we just moved into walk out basement house and we noticed that its always cold there,
Weather was Before -28 this week and door handle and windows has ice on them, What is the reason ? do we need separate furnace or the basement is not insulated properly? Thanks
Great post! What are your thoughts on air circulation? If your basement only has 3 vents and no return ducts then how are you circulating in fresh air or air that has been run through your furnace filter? Thank you.
Hi there! I live just outside of Cleveland, Ohio. We installed a new forced air system last year but did not tie in the basement. We had a mold issue previously and had it abated but didn't want to spread any spores just in case. Now we're running dehumidifiers and fans constantly and I'm wondering if I should have cut in a supply and return vent in the ductwork. Any thoughts on this? Thanks in advance!