Finishing my basement --HVAC--

[PurdueSD]

Hey guys, I'm getting ready to finish my basement. Home is a 2 story with a walkout basement underneath the entire main floor. 3.5 ton Heat Pump on the main floor and 2.5 tons upstairs. Both 4 years old. Finished basement will add ~1500 sq ft Basement will have 150 sq ft of new triple pane patio doors/ windows with southwest exposure. Home is all electric, but i do have a 250 gal propane tank plumbed into the house for attached garage heat and gas range.

1st HVAC company that suggests, zoning the basement off of the main floor HVAC. This will require 6 electric dampers, and a new supply trunk ($4500)

2nd HVAC company, suggested i need a separate HVAC, Multihead mini split was his proposal and it was ~$9K (seems excessive)

My issue with HVAC 1 is, ceilings are going to be drywalled, so access to the electric dampers in the future will involve cutting drywall. And the 2nd option, seemed like way over kill. At first he was suggesting a 3rd conventional Heat Pump.

I am planning to talk with some more HVAC guys and try to get some more input.

Basement currently has 3 supplys cut into the trunk line that i have always kept closed. No returns. I opened them to see what the temperature does down there... Staying within a degree of the main floor, with the low 80 degree weather we are seeing now.. currently -no wall insulation and poor sealing old patio doors. Both will be remedied in the remodel.

As i understand it, basements HVAC demand is more of a winter thing... and i'd like to get this project moving forward before we see cold weather set in.

Looking for any advice or suggestions!

 

[LS6 Tommy]

HVAC #1 system will be trouble. Just asking for load problems by adding to an existing system and I've never seen residential zone damper systems that work really well or didn't have issues. Just got done correcting issues with my BIL's relatively new two zone system.

Tommy

 

[cupcakemike]

I have a similar sized home as you with similar weather (i'm in kansas). I have one 4.5 ton heat pump, with propane backup for when the outside gets below 30deg, that does my 1300 sqft main floor and 700 sqft upstairs. The portion of my basement that is finished is about 1200 sqft, since 100sqft or so of it is mechanical room.

Our master is upstairs and does get a bit warm in the middle of the day when its 90deg+ outside, like 75/76 when the t-stat is set at 72. Our master has 40 sqft of south facing glass and is as far away as you can get from the air handler and sitting directly above our (unconditioned) 2.5 car garage with 14ft ceilings and a south facing wall of glass (80 sqft) -not to mention that the t-stat is also about as far away from our master as you can get.

Regardless, I have 6 supplies in my basement and 1 return (if you have your air handler in the basement, it shouldn't be hard put a return in the basement). When I finished the basement I put a sliding glass door on one end of the walkout (to exit a bedroom) and a man door on the other side of the walkout, at the end of the hallway. There is an egress window in the middle of the walkout to allow exit from the other bedroom. I have 2 18x36 casement windows, not large enough to qualify as exits, in the main family room and in the theater room. I simply insulated with 1" foam board when I furred out the walls for drywall.

The first couple years I kept the registers open in the basement and, like you, temp stayed fine in there, if nothing else a bit cooler in the summer (obviously since the air is dumped to the basement first, before going to the rest of the house via duct work, due to the air handler's location). Anyway, After a couple years I tried an experiment to see if I could help cool our master a little bit more and closed off all the registers in the basement. Guess what, our master got a bit cooler (more air going to it) and the basement temp was basically completely unchanged, no matter what was happening outside. Also, we installed relatively cheap thermal/blackout curtains on all the windows at this time to try to limit heat gain/loss.

My HVAC guy told me that in most cases that don't even consider the basement in the calc for cooling/heating because as long as its not one of those "daylight" basements, that are only a couple feet in the ground, the earth does such a good job of insulation you don't really see temp swings.

Take it for what its worth, but in my opinion you don't need to install extra HVAC for a basement.

 

[smarthoyboy]

Are you planning on doing interior partitions in the basement? Will it be extra day-to-day living space, party/gathering space storage, or workshop?

I never seen good results with the residential dampers as mentioned above. Inducing airflow through the basement may just fit the bill, depending on usage. If anyone, a single zone mini-split may be all you need to take off some of the edge.

Sent from my ONEPLUS A6013 using Tapatalk

 

[PurdueSD]

HVAC #1 system will be trouble. Just asking for load problems by adding to an existing system and I've never seen residential zone damper systems that work really well or didn't have issues. Just got done correcting issues with my BIL's relatively new two zone system.

Tommy

Thanks for the perspective... zoning has been around forever and i think i would be more open to it if we would have access through a drop ceiling to the electric dampers... Behind drywall just seems like you're asking for a pita.

I have a similar sized home as you with similar weather (i'm in kansas). I have one 4.5 ton heat pump, with propane backup for when the outside gets below 30deg, that does my 1300 sqft main floor and 700 sqft upstairs. The portion of my basement that is finished is about 1200 sqft, since 100sqft or so of it is mechanical room.

Our master is upstairs and does get a bit warm in the middle of the day when its 90deg+ outside, like 75/76 when the t-stat is set at 72. Our master has 40 sqft of south facing glass and is as far away as you can get from the air handler and sitting directly above our (unconditioned) 2.5 car garage with 14ft ceilings and a south facing wall of glass (80 sqft) -not to mention that the t-stat is also about as far away from our master as you can get.

Regardless, I have 6 supplies in my basement and 1 return (if you have your air handler in the basement, it shouldn't be hard put a return in the basement). When I finished the basement I put a sliding glass door on one end of the walkout (to exit a bedroom) and a man door on the other side of the walkout, at the end of the hallway. There is an egress window in the middle of the walkout to allow exit from the other bedroom. I have 2 18x36 casement windows, not large enough to qualify as exits, in the main family room and in the theater room. I simply insulated with 1" foam board when I furred out the walls for drywall.

The first couple years I kept the registers open in the basement and, like you, temp stayed fine in there, if nothing else a bit cooler in the summer (obviously since the air is dumped to the basement first, before going to the rest of the house via duct work, due to the air handler's location). Anyway, After a couple years I tried an experiment to see if I could help cool our master a little bit more and closed off all the registers in the basement. Guess what, our master got a bit cooler (more air going to it) and the basement temp was basically completely unchanged, no matter what was happening outside. Also, we installed relatively cheap thermal/blackout curtains on all the windows at this time to try to limit heat gain/loss.

My HVAC guy told me that in most cases that don't even consider the basement in the calc for cooling/heating because as long as its not one of those "daylight" basements, that are only a couple feet in the ground, the earth does such a good job of insulation you don't really see temp swings.

Take it for what its worth, but in my opinion you don't need to install extra HVAC for a basement.

Thanks! Im pretty positive i don't need to for the summer months. Opening the 3 supplies and (no returns yet, no insulation) has the space really comfortable on 90 degree afternoons... Even with the leaky old patio doors. Im more concerned about it being warm enough down there in the winter.

 

[PurdueSD]

Are you planning on doing interior partitions in the basement? Will it be extra day-to-day living space, party/gathering space storage, or workshop?

I never seen good results with the residential dampers as mentioned above. Inducing airflow through the basement may just fit the bill, depending on usage. If anyone, a single zone mini-split may be all you need to take off some of the edge.

Sent from my ONEPLUS A6013 using Tapatalk

Nope it will be an open floorpan with a closet under the stairs out near the middle of the room. Wet bar adjacent to large tv/ couch area on one end.

Game room on the other. Pinball, Air Hockey, pop a shot etc.

One walled off 9'x20' clean storage/ mechanical room/ Electrical Panels. (This room will have a drop ceiling)

 

[yeldogt]

First ... you have to get loads done. What's the heat load .. how much are you adding?

W/O back up heat -- you must have decent HP's installed. 6T is a lot of power -- I can't believe adding more is the answer ... Unless the load calculation shows a demand.

Doing a walk out basement typically is about air flow in the summer -- the loads in the winter are a bit more .. but, nothing like a first floor ... especially if you have batt insulation.

Zoning works ..... I grew up in a zoned house done in the 50's -- by my parents .. way before I came along. It's math .. how much does each room need .. add it up to get the full load on the structure. Go back to room loads and figure out what duct size needs to go to each space and where. With one speed equipment -- understand what is the minimum flow. with VS equipment design the smallest zone to take +25% (max) of minimum flow of equipment. design trunks to feed.

Is the HP air handler in the mechanical ? No way to design two trunks -- with outlets spaced along this trunk ... keep the two vent dampers in the mechanical ?

There are different types of dampers and all use an external motor -- the damper themselves typically don't fail ... especially the on/off with single damper. Sometimes you have to do what's required -- marking accurately for location -- if you are unlucky -- cover hole with fake recessed light if you ever have to cut in. I have not had a failure in years .... but the second you burry something ?

The idea of a mini .. is not a bd idea. Again, its all about "what's the load" .. I'm doing a supplemental Mini in the lower level of my new build .. the house has both HP's and radiant .. in the shoulder seasons when the radiant is not running .. I'm seeing the possibility of it being cold in that spot in the AM. It's over kill -- but with everything new .. I'm risking the 4k.

You could always do the duct work .. and if it's not perfect on the coldest days. Add a Mr/ Cool DIY ..... also don't discount supplemental resistance heat. Installing quality baseboard electric heat is cheap/simple and very nice heat (and fast) .. as an add on you will not need much. They even make panels .. it's obviously more expensive to run .... but, how much and how often will you need to use it ? 5k -- .. buys a lot of electricity.

 

[PurdueSD]

First ... you have to get loads done. What's the heat load .. how much are you adding?

W/O back up heat -- you must have decent HP's installed. 6T is a lot of power -- I can't believe adding more is the answer ... Unless the load calculation shows a demand.

Doing a walk out basement typically is about air flow in the summer -- the loads in the winter are a bit more .. but, nothing like a first floor ... especially if you have batt insulation.

Zoning works ..... I grew up in a zoned house done in the 50's -- by my parents .. way before I came along. It's math .. how much does each room need .. add it up to get the full load on the structure. Go back to room loads and figure out what duct size needs to go to each space and where. With one speed equipment -- understand what is the minimum flow. with VS equipment design the smallest zone to take +25% (max) of minimum flow of equipment. design trunks to feed.

Is the HP air handler in the mechanical ? No way to design two trunks -- with outlets spaced along this trunk ... keep the two vent dampers in the mechanical ?

There are different types of dampers and all use an external motor -- the damper themselves typically don't fail ... especially the on/off with single damper. Sometimes you have to do what's required -- marking accurately for location -- if you are unlucky -- cover hole with fake recessed light if you ever have to cut in. I have not had a failure in years .... but the second you burry something ?

The idea of a mini .. is not a bd idea. Again, its all about "what's the load" .. I'm doing a supplemental Mini in the lower level of my new build .. the house has both HP's and radiant .. in the shoulder seasons when the radiant is not running .. I'm seeing the possibility of it being cold in that spot in the AM. It's over kill -- but with everything new .. I'm risking the 4k.

You could always do the duct work .. and if it's not perfect on the coldest days. Add a Mr/ Cool DIY ..... also don't discount supplemental resistance heat. Installing quality baseboard electric heat is cheap/simple and very nice heat (and fast) .. as an add on you will not need much. They even make panels .. it's obviously more expensive to run .... but, how much and how often will you need to use it ? 5k -- .. buys a lot of electricity.

Thank you!

First off... yes the HP/ air handlers were middle of the road Carrier units when purchased 4 years back... 16 seer and variable speed blowers. Electric backup resistance heat. They have been trouble free and perform well on the coldest/ hottest days. Well... other than the meter spinning... one month/ winter thanks to the electric strips.

2nd... getting a contractor around here to do a heat load on anything that isn't new construction is like pulling teeth. Ive been through remodels and new equipment before with a dozen different local companies over the years and i never get anywhere with heat calc. They always have excuses like we didint design the original system, cant access it to see what's there... its not necessary etc. It *****, but its the way it is.

I plan to insulate really well which includes spray foaming the rim joist, and replacing the patio doors and windows with efficient well sealed ones. Should be a nice tight space.

My house footprint is on a 30 degree angle, with the main floor air handler sitting in the basement right under the angle. The supply and returns T off the air handler in both directions. And there is several supply runs very close to the air handler... They make a single damper to another trunkline not possible. Hence the need for multiple (6 ish in total) dampers. There is room for another trunkline but it is out past a block wall partition that is past several of the supply runs in the existing trunkline. Hopefully i did a good job explaining that.


I don't really have too much of a concern about whether we can handle the basement with the equipment we have.... I would be completely onboard with zoning it if it were a couple dampers in the mechanical room, but its not that simple. I believe based on what i'm seeding this summer with temps down there... that the room can easily be heated and cooled sufficiently with 5 or 6 supply runs that have adjustable dampers... and adding a couple returns. But i am cautious about air flow being sufficient. But the basement is very dry and has a water proofing system in place that has completely eliminated most any of the dampness that was down there.

My guess at this point is that i will go with the add additional supply runs... with flex runs out to the appropriate areas and 2/3 returns off the main trunk lines to try to balance the main floor/ basement with the manual register dampers. If i cant get it quite perfect im ok with that. If i run into trouble , add a mini to supplement down the road.

Again, i wish i had better success getting HVAC guys to do a heat load... i'm trying and know that's what i need. Happy to share some pics or more information if you're interested understanding what i have going on!

 

[hmbemis]

I've got a raised ranch -- the basement is ~4' below grade at the front, and at grade in the rear -- Technically I've got 2-3 registers down there, but they barely dribble air. In the summer w/ the central air running the basement is actually too cool for our taste, nearly all the cool air ends up settling. I've got relatives w/ the same style house but w/ retro-fit central air in the attic, so only registers upstairs, their basements are comfortable too.

I don't know that I've even bother to attempt to cool the basement, I think you'd be better off with a dehumidifier that can be run in all seasons, and then focus on how to provide heat down there in the winter which might be electric baseboards since I'm going to to assume that the ROI on baseboards vs. heat pumps will end up favoring the baseboards when you factor initial costs and maintenance along side operational.

 

[bobbyjean]

use the three supply hits you already have and add ductless units -not sure of your floor plan...if you are below grade in any of the basement that will be conditioned it should be figured in,is humidity a concern there-go with a name like fujitsu,mitsubishi,daiken for low temp heating operation-check the specs and you will see the drop off on capacity at low ambients. look into ducted mini splits if your layout will allow-just my 2 cents

 

[LS6 Tommy]

I have a Fujitsu Halcyon in my basement. It runs on "Dry" pretty much from spring to fall and I really didn't see an appreciable increase in energy usage. It actually went down from the previous season of running a duhimidfier, which made the basement even warmer.

Tommy

 

[sr71]

IMHO - Spend your HVAC budget on something else. Even with cold Michigan winters my finished basement is only a few degrees cooler than my main floor (year round) ...but very livable. To be fair my home (ranch) has radiant heated floors throughout the main floor so perhaps there is some radiant energy that finds it way downstairs rather than just flowing up.

Assuming you plan to entertain in the basement - sports, parties etc., the slightly lower temp is perfect.

 

[Jackfre]

I'm with Tommy on zone dampers. Do they work? Sure, maybe, sometimes. Are they compatible with what is there and the stats. That is not to be overlooked. I'd do the mini-split. In am open floor plan you should not need a lot of evaporators.
My concern would be with the sheet rocked ceiling. Basements are built and looked at during construction as an open mechanical area. Power, plumbing, hvac, internet, etc all over the place. The sheet rocked ceiling may look better, but I think over time you will be happy that you did a dropped ceiling. Keep in mind that if it can go wrong, it will go wrong. If you go forward with the rock I would suggest that you have detailed photos and dimensions to services.

 

[PurdueSD]

I'm with Tommy on zone dampers. Do they work? Sure, maybe, sometimes. Are they compatible with what is there and the stats. That is not to be overlooked. I'd do the mini-split. In am open floor plan you should not need a lot of evaporators.
My concern would be with the sheet rocked ceiling. Basements are built and looked at during construction as an open mechanical area. Power, plumbing, hvac, internet, etc all over the place. The sheet rocked ceiling may look better, but I think over time you will be happy that you did a dropped ceiling. Keep in mind that if it can go wrong, it will go wrong. If you go forward with the rock I would suggest that you have detailed photos and dimensions to services.

Thanks for the perspective. I've always done drop ceilings in basements my whole life... and yes they are great from an accessibility stand point. My father built custom homes and ingrained it into my head.

Honestly, I'm at the point of my life where a drywall ceiling repair wouldn't be the end of the world. I'm willing to take the trade off for a space that seems less like an office building and more like the rest of my home. Detailed pictures are a great idea! There will be no mechanicals buried, as long as i avoid the mechanical dampers. The air handler will be back in the mechanicals closet. So essentially i will only be burying electrical, plumbing, ducting, and the HVAC lineset. All of which I have buried in the main floor and upstairs of my home already.

The only issue i am a little concerned with being Cable TV and LAN setup. A friend, who is in the IT industry, is helping me try to future proof my setup before i restrict future access.

 

[fitter30]

Basement going to be entertaining might want to consider a mini. Couple of ceiling fans should work with a single head. Damper system have never seen one work right.