Basement dehumidifier / cooling

ChrisJ

I use my basement for a lot of things and need to keep humidity low.  Unfortunately due to the stone foundation and partial dirt floor there's plenty of humidity to squeeze out of the air.


I've been using a 50 pint typical dehumidifier since 2011 and it keeps it around 40%.  The problem is it heats the basement as well.  My temperature ends up around 80-82f during the summer.

While this isn't terrible it's also encouraging more evaporation from the dirt and walls I'm sure.

What area my options as far as equipment?  Does anyone make a mini split with some kind of partial reheat?

Right now I'm considering adding a 2 hose portable AC with the current dehumidifier.  Then they can work together but I'm wondering if there's a better solution.

The window style won't allow a window unit.  I'm guessing I need about 5-6kbtu. 


No, finishing the floor and sealing the walls isn't in the cards right now.  

pecmsg

Just the smallest mini split you can find. 

Single systems start at 9 Or 12K and are too large. A duel zone 12 upstairs and 6 in the basement works much better. 

ChrisJ

pecmsg said:

Just the smallest mini split you can find. 

Single systems start at 9 Or 12K and are too large. A duel zone 12 upstairs and 6 in the basement works much better. 

Upstairs is served by a 2 stage 3 ton split unit and it's near perfect so there's nothing to spare for the basement.

Do any minis have a hot gas reheat option of any kind?

ratio

IDK if it'd be cost-effective, but maybe a wine-cellar unit? The one I installed was nothing more than a walk-in-cooler style condenser with built-in head pressure control; & a bog-standard air handler. This one didn't have reheat, but other models did, for even better dehum.

JUGHNE

All the newer crawl spaces I have worked in had the floor covered with VP poly that ran up the walls to the floor above.
Yes would be a PITA for you to walk on, as it was to crawl on. So they eventually would put a couple inches of sand on the poly.
This held it in place from walking around and protected the poly.

Is there any way you could sneak even just a 6" run down thru a closet or chase from the AC?
In these crawl spaces I would put maybe 2 runs and treat it as a conditioned space.
Seemed to make the place tolerable.

If I recall your 3 ton was a bit over the building needs.

ChrisJ

JUGHNE said:

All the newer crawl spaces I have worked in had the floor covered with VP poly that ran up the walls to the floor above. Yes would be a PITA for you to walk on, as it was to crawl on. So they eventually would put a couple inches of sand on the poly. This held it in place from walking around and protected the poly. Is there any way you could sneak even just a 6" run down thru a closet or chase from the AC? In these crawl spaces I would put maybe 2 runs and treat it as a conditioned space. Seemed to make the place tolerable. If I recall your 3 ton was a bit over the building needs.

No, the 3 ton was never over the houses needs.  I think others on here claimed that in their opinion it was too big, but it won't hold it's set point above 92 or so outside, depending on the dew point of course.   But during a heatwave of 95 it'll end up 2 or 3 degrees above setpoint.  My opinion is it's about as perfect as it can be.

That  aside, while I'm not sure about my thoughts on radon concerns id also rather not encourage it to come into the living space more than it already does.

pecmsg

Forget the upstairs system. 

Whole house dehumidifier 

ChrisJ

pecmsg said:

Forget the upstairs system. 

Whole house dehumidifier 

But that won't provide any cooling will it?

JakeCK

You have two options, throw more energy at it or seal the floor and walls. You have already said sealing isn't in the cards so throwing more energy is your only option. Getting a portable ac would be the cheapest. Run the hose to a window, or put in a vent through a wall. 

Edit: wow I some how missed the part where you said you use a portable ac. :S yup that's really the only affordable option.

Water proofing from the outside can and will help a lot. And of course the low hanging fruit. Make sure all the run off from the roof can get away from the house quickly and any storm drains are free flowing. With a stone foundation installing foam board isn't a great option. Spray foam will work. The basement floor is difficult since I'm guessing you already have a low ceiling. 

All of these options are big $$$$$ money tho.

Jamie Hall

Remember that to dehumidify you need to cool the air to the desired dewpoint -- which may be remarkably low. Then to be comfortable, you will have to reheat. Dehumidifiers do that -- the exhaust air is rewarmed by blowing over the condenser coils, or at least part of it is. If you want it at 40% with an air temperature of 70, perhaps, the dewpoint is about 45. So you want your dehumidifier to pull it down to that. Now... the dehumidifier will raise the air temperature, since its efficiency is less than 100%, and the excess energy shows up as heat and warmer air.

So. you need to cool the whole show. I like your idea of the small portable air conditioner. Sounds like exactly the right gadget.

ethicalpaul

Replace that gas hot water heater with a heat pump one

1. The heat pump water heater will help to dehumidify (not as much as you need, but still)
2. You will no longer be getting negative pressure from your gas water heater's flue, pulling warm moist air into the basement all summer.

ChrisJ

@Erin Holohan Haskell

May I request a temporary exemption from the forum rules and etiquette to respond in an appropriate manner to my friend @ethicalpaul ?

To be specific, I would like to use several colorful metaphors, giving him a specific location I would like him to place his heat pump water heater......

pecmsg

Another option is a whole house dehumidifier with outside air hookup. Keeping the envelope slightly positive will aid the other 2 systems. 

JakeCK

Well ethicalpaul isn't technically wrong. It will help, but not nearly enough to resolve your problem. Lol

mattmia2

Maybe looking at dehumidifier efficiency is part of the fix for this. If it uses less energy then it adds less heat to the basement. Are there small desiccant type humidifiers? They dump their heat outdoors.

ethicalpaul

JakeCK said:

Well ethicalpaul isn't technically wrong. It will help, but not nearly enough to resolve your problem. Lol

So you mean what I said was exactly right, thanks!

Does anyone else think that a constant open flue with occasional combustion is drawing in warm moist air, or was I wrong about that one--honest question thanks!

mattmia2

ethicalpaul said:

Does anyone else think that a constant open flue with occasional combustion is drawing in warm moist air, or was I wrong about that one--honest question thanks!

It is but it is negligible compared to the infiltration around the sill.

ChrisJ

My water heater is a power vent.  There's no open flue


@mattmia2 the only desiccant type dehumidifiers I know of a joke?  Like damperid?   

mattmia2

ChrisJ said:

@mattmia2 the only desiccant type dehumidifiers I know of a joke?  Like damperid?   

No. they use a desiccant wheel and heated outdoor air to regenerate the wheel and dump the humidity and heat outside. Look at if the efficiency is still reasonable in a humid climate.

https://ecor-pro.com/desiccant-dehumidifiers/

There are a number other manufacturers too.

ethicalpaul

mattmia2 said:

ethicalpaul said:

Does anyone else think that a constant open flue with occasional combustion is drawing in warm moist air, or was I wrong about that one--honest question thanks!

It is but it is negligible compared to the infiltration around the sill.

I would say it helps make the sill infiltration much worse. It creates a negative pressure that pulls more air through the sill (and other leaky spots). That was my point if I was unclear, sorry. But my point is moot because he has a power vent. Thanks!

JakeCK

If you have more air coming through the sill than what goes out a 6" or so flu attached to a 20, 30, or 40ft+ stack... Well you got problems. Go buy yourself a can of expanding spray foam and get to em'. I did have that problem at one point and I hunted them all down on a very cold winter night. A damp hand when 25f air is blowing across it is pretty good at detecting those leaks. 

ethicalpaul

the air coming into the house is going to at least equal what is going out the 6" atmospheric flue, by definition, no? That's why I think it's a bonus to be able to eliminate it.

STEVEusaPA

mattmia2 said:

ChrisJ said:

@mattmia2 the only desiccant type dehumidifiers I know of a joke?  Like damperid?   

No. they use a desiccant wheel and heated outdoor air to regenerate the wheel and dump the humidity and heat outside. Look at if the efficiency is still reasonable in a humid climate.

https://ecor-pro.com/desiccant-dehumidifiers/

There are a number other manufacturers too.

I've seen them used with radiant cooling. Of course not here, but in Germany.