Figured this was the best spot for this.
Getting ready to finish off about 700sgft of my 1600sgft basement. The other 900sgft is a work shop/mechanical room and storeage, all of which are closed off from the soon to be finished area with doors. House is a 1600sgft ranch.
Finished area is gonna be pretty much just a TV/hang out room and a half bath, nothing too fancy.
House is 14 years old and we are in S/e lower michigan. In the summer our basement gets that musty smell and I have a stand alone dehumidifier but it runs pretty much none stop (loud, adds heat etc).
Looking for a better solution to make the space enjoyable when I’m done. Basement walls are 6inch poured, no leaking cracks, I have a sump, never had any water in the basement in the past. They will be fiinshed with stud walls and foam sheet insulation between the poured walls and the studs.
House is pretty tight and there is a make up air duct from the outiside into my cold air return and a combustion air duct from the outside that runs next to the furnace (85% AFUE). I know both of those ducts have baffles that open/close depending on use. Laundry is on main floor, not in the basement.
I know stuff like the fans that go in the joist bays and blow in and out are snake oil or atleast wont work where i’m at. The basement is not too bad when the central air is running but we usually only need it about 2 months out of the year.
What do you guys suggest or an I kinda screwed? Willing to listen to any possible solutions that dont cost 10k to install lol.
Thanks and happy new year!
J-
Replies
1. Buy a quieter dehumidifier, newer models 40 dB quieter than 90's models
2 I you have a sink in the basement, it is not aesthetic but works - hang 3 pair of old pantyhose filed with calcium chloride above the sink, very hydroscopic, water will drip off and down the sink. Pop used that in the 40's and 50's in our basement, would fill a coal bucket with water every 2 days from just one full leg of a nylon stocking. Noiseless but messy.
3. Build a ducted sound deadening box around your dehumidifier, For the air inlet and outlet, cut 14" lengths of 1/2" thinwall PVC pipe and stack into a bundle for a muffler. A square foot bundle works well, with a right angle duct at each end with duct wall being fiberglass lined.
4. For heat, you just about have to build your own spit system dehumidifier with part of the condensor outside. (aka your air conditioner)
Soemone wil likely point out you can get lung disease from calcium chloride dust. So, you do not want to grind it up and spread the dust around the house, leave it confined to the inside of stockings.
Basements are NOT Intended as Living Spaces
That's the first thing you must realize. A basement is simply a hole with a house atop it.
The reason basements ar damp is because ... they don't get enough air. Trapped air enters, cools, and the moisture drops out. With nowhere to go, the basement gets damp.
Those little windows? They're only there to meet code requirements, and don't let nearly enough air circulate.
Your household HVAC was never designed, sized, or ducted to include the basement. Adding a finished basement nearly doubles the amount of air the system needs to handle. Even if you re-did the ducting, the system can't move all that air.
So ... what to do? Well, the first thing is to make sure all moisture has some place to go. Floors need to slope to the drains .... basement floors are not nearly as flat as you might think. Place your face to the floor and look - it's nowhere near as flat as your driveway. The sump is likely the highest point (the sump tends to rise / float up as the concrete cures).
The next step is to instal a completely separate HVAC system for the basement, including individual temperature control and dedicated make-up air.
The solution you dismiss - a humidity-controlled fan with dedicated make-up air - is actually a solution that works. Such systems usually have one duct bringing in fresh air, and a duct drawing stale air from a point remote from the intake. The idea is to circulate the air within the basement.
There are duct fittings intended to transfer heat from the out-going air to the fresh incoming air.
Finally, concrete is porous. Water comes right through it in vapor form. There's nothing you can do to stop this. You can, however, keep room moisture from condensing on it with your construction methods. Your first defence is to pump this moist air out before it can condense.
Space your finished walls off of the basement concrete. Drywall suppliers sell "hat channels" for this very purpose. A little insulation - say, 1/2" R-Max foamboard - goes a long way. Make sure there's a 3/4" gap between the wall coverings and the floor (you can hide the gap with plastic molding). Cover your floor with rubber-backed carpet tiles, or a 'floating' floor such as Pergo.
High humidity is result of the basement being much cooler than ambient air. Deep soil temperature in your area is ~50F. A bare concreate basement floor will approach that temperature.
Insulation is your friend. Insulate all of the basement, floors and walls, and the humidity problem will be much reduced. Floor insulation does not have to be complicated, DriCore or similar products can be used as is for the unfinished area.
Make sure the sump is sealed.
A small high efficiency dehumidifier will take care of the rest. Your heating bill will also go down.
Cheers,
I just completed my own basement which had simiar issues (damp/moist but no active leaks). Rigid insulation on all exteriror walls and thermafiber into the joist bays helped a lot then a 1-inch gap folowed by 2x4 framed walls I used dense armor plus instead of drywall.
I didnt have the headspace for insualtion on the floor so we went with vinyl plank flooring which is supposed to tolerate moisture. Lastly I replaced my room sized dehumidifier with a whole house style ducted unit from Siemens at $1000. I run the unit in the basement only it's fairly quiet and does not cycle constantly. It runs through July and August and sucks a lot of water out of the air. The basement was done 2 years ago no smell and no issues...