Wow, that uses a lot more energy then I thought!

delcrossv

Wandering back onto the topic, If the OP has efflorescence, he really needs to address that by sealing the outside of the foundation. Locally there was a company that would spray a mixture of asphalt and shredded fiberglass (the applicator was really neat- two spools of glass rope would autofeed into the gun and be shredded and mixed with the asphalt). That and new exterior drain tile tied to a sump and the humidity dropped significantly. No leaks for 25 years and counting.

PC7060

I put my dehumidifier on a timer and it runs for six hours at night. The humidity level is set to 40% so it pretty much runs consistently for the six hour period. It makes a big difference bring the level down to mid 40s through the house, and it’s nice not to have to listen to it during the day.

JakeCK

With an unlimited budget yes I would also waterproof and insulate the exterior of the foundation. But that would probably cost in the ball park of $50k with today's prices. 

Efflorescence is just the minerals left after the moisture has evaporated from the foundation. Which is ironically accelerated by the dehumidifier. It's the continuous movement of moisture that is causing the problems. Sealing the foundation in with a insulated vapor barrier will stop that continuous movement of moisture and also stop the evaporation of the moisture that is already there. No more efflorescence. The foundation will now be outside the building envelope. And concrete and masonry doesn't care if it's wet or damp. 

The vapor impermeable insulation will also be at or very close to room temperature ensuring it is above the dew point. Like is said in the op, the science says it works. I'm just really looking to see if anyone has done exactly this before.

Edit: None of this applies if one has issues with actually running water weeping out of the foundation. That is an entirely different ballgame. I luckily do not have that problem on the foundation. My only liquid water issues is with the collapsed storm lateral, and the front porch leaking from above. Both of those are going to be corrected this spring/early summer. The whole front porch and steps are getting rebuilt. And that lateral getting repaired. 

hot_rod

Have you done a radon test?

JakeCK

hot_rod said:

Have you done a radon test?

No. I might once I seal it up.

JakeCK

People exhale CO? Sorry just poking fun.

ChrisJ

A lot of the heat from a dehu is needed to reheat the air but there is quite a bit of waste heat. My basement runs a good  5 to 10 degrees warmer from it 

You'll notice when the latent load is high the air leaving the unit isn't room temperature it's actually quite warm.

JakeCK

@ChrisJ mine too. My basement will be in the 80's all summer long from mine. I keep the upstairs in the mid 70's in the summer. And that is heat that my AC then needs to work to remove. So many synergies that can happen by getting the infiltration of humidity under control. Between the energy used to dry and heat the air, the energy used to run the HPWH, and the energy used to cool the house. 

JakeCK

So something interesting happened this evening... The dehumidifier has stopped running. I know I just emptied it so it's not full, and it would report as such anyways in the app. I can see that it is on too. Humidity is holding at 62% and it is set at 60. 

Thats honestly a little higher than I would like but... It didn't shut off when I set it to 60, it shut off when I left the house for work. What changed? One thing I did was close all the doors on the second floor. The wife and kids are at her parents house for the night. (Our work schedules don't work together very well and this saves her from having to wake them up at the crack of dawn) Closing all the doors is a habit I developed over the past year to keep the cats out of the bedrooms and bathroom when we're not home. One of them is a trouble maker. It also had the benefit of reducing run time on the boiler all winter. 

Still want to do the 1sqft plastic test on the foundation but this is a strong indicator of where the problem is. 

I walked out the door at 5pm, the water heater shut down around 6. You can see where power consumption drops shortly after I walk out the door and again when the HPWH shuts down. As long as that doesn't turn back on I'll see a gradual decrease in power consumption from the aquarium lights dimming and shutting off untill it bottoms out around 295-320watts. There will still be small spikes for the fridge and freezer periodically, and if it's cold enough for both the boiler and aquarium heater. 

Edit: I wish I knew what the actual temperature is in the basement. That's one part of the house that isn't monitored like the rest. The garage is at 64% and at 66f. And it's currently 56f @ 84% outside, dew point is 52f. So it might have just shut off because of the change in weather too. But I would think all the rain we just got would have made it worse...

EBEBRATT-Ed

Yes as @Jamie Hall pointed out the heat is not wasted. Don't forget we are talking Relative Humidity. 50% RH at 60 degrees is a different moisture content that 50% RH at 70 degrees and the dew point changes with that as well. Different than absolute humidity

That's why in humidity-controlled rooms, labs etc they use steam, hot water or electric re heat. Basically, on a call to lower the humidity you run the ac balls out to dehumidify then reheat the air to room temperature with the reheat. This is an energy pig and is only allowed in labs and other humidity-controlled rooms..computer rooms etc. But with a house humidifier I guess the heat is free

As @hot_rod mentioned a garage floor company. In the old days to seal a room they recommended epoxy paint.

The trick is will it stick to the walls

ChrisJ

EBEBRATT-Ed said:

Yes as @Jamie Hall pointed out the heat is not wasted. Don't forget we are talking Relative Humidity. 50% RH at 60 degrees is a different moisture content that 50% RH at 70 degrees and the dew point changes with that as well. Different than absolute humidity

That's why in humidity-controlled rooms, labs etc they use steam, hot water or electric re heat. Basically, on a call to lower the humidity you run the ac balls out to dehumidify then reheat the air to room temperature with the reheat. This is an energy pig and is only allowed in labs and other humidity-controlled rooms..computer rooms etc. But with a house humidifier I guess the heat is free

As @hot_rod mentioned a garage floor company. In the old days to seal a room they recommended epoxy paint.

The trick is will it stick to the walls

Like I said,

There is some waste heat.
Also, wouldn't labs take advantage of hot gas reheat?

mattmia2

Jamie Hall said:

Problem with that is that the heat isn't wasted. The whole way in which dehumidification works is that the air is cooled to the dewpoint corresponding to the relative humidity at the desired air temperature, and then reheated back to the desired temperature.

Plus a fair bit of energy to move that heat.

Jamie Hall

If one runs through the energy balance for residential type systems carefully there is indeed a small amount of excess heat if one considers only the dehumidify cycle as a closed system. That is the heat released when the moisture is condensed as the air is chilled to the dewpoint. There is also the heat involved in the less than 100% efficiency of the compressor related to the refrigerant cycle. In a well designed system, most of this latter heat will be captured, however, in the reheat section. In most situations, however, the dehumidifier is not, in fact, a closed system. Rather, it is part of a more extensive space -- such as a basement. In such a space, there is also the heat required to evaporate the moisture from, for example, the walls in the first place. This will cool the air in the space; the heat recovered by condensing in the chiller section of the dehumidifier will replace that heat loss.

Then if one considers the possibility of infiltration, one must account for the latent and sensible heat in that air flow...

Or, going a bit further, does one need to account for the latent hear released when moisture condenses outside to produce the liquid water which then seeps through the basement walls?

Oh dear... things can get so complicated...

Bottom line. Residential or similar dehumidifiers are energy hogs, as this thread suggests. Just as in heating (or air conditioning) the place to start is with controlling the air (sensible and latent heat) and, in this case, moisture flows from outside the target space.

As @EBEBRATT-Ed noted, in critical applications one takes a somewhat brute force approach to the air in the specific space -- but there's nothing to prevent one from building back some efficiency elsewhere.

reggi

I guess everyone has their system and I've found due to the basement being cool the dehumidifiers efficiency was suspect ( I forget the actual temperatures) that ... For me... keeping the windows and doors closed keeps the basement comfortable..
Perhaps just a quirk of insulation projects (above foundation)  and keeping up with repairing areas that the concrete gets flaky as I get to it.. I guess I could fire up the boiler to get the moisture down if need be until the header gets to hot to touch 

EBEBRATT-Ed

@ChrisJ

Hot gas reheat was not common in my time, but I know Trane and others (AAon I think) have that available in a package unit. I don't know about split systems with air handlers.

For labs etc they used to say a split system was better than a packaged unit because packaged unit are typically designed to remove 75-80% sensible heat and 20-25% left for humidity removal.

With a split system you could play with the fan speed etc to get the sensible ratio where you want it. At least that was the common approach with belt drive AHUs or with VFDs. With a split you can mix and match condensing units with evap coils to get what you want to hit design.

JakeCK

Jamie Hall said:

Oh dear... things can get so complicated...

Yes they can.

I just want my basement to stay subtropical and mold free. With out expending gobs of energy to do it. Is that so much to ask? Lol

Jamie Hall

JakeCK said:

Jamie Hall said:

Oh dear... things can get so complicated...

Yes they can.

I just want my basement to stay subtropical and mold free. With out expending gobs of energy to do it. Is that so much to ask? Lol

No -- very reasonable request. Problem is, as you have noted, it may take a surprising amount of power to do!

Solid_Fuel_Man

Once you figure out if it is safe to do so... 

I'd not use polyiso in a damp location. XPS like BlueBoard would be my choice. Polyiso is great for framed wall insulation or roof insulation, but water will infiltrate it. 

My choice for a basement wall would be a nice 8mil or thicker plastic sheet, then an inch or more of blueboard over that. 1" of XPS is an R5 which would get you well over the dewpoint. I would overlap the plastic at least a foot and tape the lap joints with a building tape. Then fasten the XPS mechanically with Tapcons or better yet stainless steel RamSet nails through strapping. Then put a protective layer of sheetrock if code dictates, or plywood to hang stuff on etc. 

I'd do the same for the floor, rather than strapping just lay the plywood directly over the XPS and RamSet through the assembly. 

JakeCK

The moisture is coming in from air infiltration I think. Since the temperature went back down into the 30-40s with highs bumping into the 50s the basement has been staying around 45%. If it was coming from the foundation I wouldn't imagine it would swing so wildly with the outside temperature. 

Also this is a terracotta foundation, tapcons and nails are a no go. It'd be like driving a nail through a clay pot. And people have done it in the past. Leaves nothing but a giant hole.
Anything secured to the wall need to be glued and/or very carefully screwed into the mortar joints.

mattmia2

You can put a tapcon or rawl plug in it if you are careful for small things, but you really need to get a toggle in to a core for big loads.

JakeCK

mattmia2 said:

You can put a tapcon or rawl plug in it if you are careful for small things, but you really need to get a toggle in to a core for big loads.

When I gutted it about 10 years ago that was how a couple of the outlet boxes were secured to it. They left a pretty big hole, about an inch, maybe a bit bigger in diameter. They had to use beefy toggle bolts just because of the size.

That would be over kill for foam insulation. Not to mention on heck of a hole though the foam it's self. Why I was thinking about glueing it to the foundation and nailing it just to the sillplate. A large percentage will eventually be covered by 2x2 framing and drywall anyways. 2" polyiso and 2x2 dimensional framing comes out to exactly a 2x4 wall.

mattmia2

Glue is probably the way to go for insulation. It seems to get crumbly if it has been wet for a long time. You have to be careful how you tighten the tapcons or you will strip them. It helps to put them in a web too. At work i was mounting some equipment behind a display on structural clay time that was plastered, i started with tapcons and ended up putting plugs and screws in the holes from the tapcon masonry drill. I wonder if you could somehow secure to it by skimming mortar in to the keys on it.

Solid_Fuel_Man

Oh, I missed that it was a terracotta foundation. Never have seen that before in my travels. Just, stone, block, pressure treated lumber, and poured concrete. Terracotta is a new one to me. 

I would still avoid polyiso, it doesn't do well with water. 

mattmia2

Solid_Fuel_Man said:

Oh, I missed that it was a terracotta foundation. Never have seen that before in my travels. Just, stone, block, pressure treated lumber, and poured concrete. Terracotta is a new one to me. 

I would still avoid polyiso, it doesn't do well with water. 

It is technically called structural clay tile. It was mostly used around the teens and 20s. There is a lot of it here in ann arbor. I suspect because it was used a lot for university and commercial buildings so it was available. You see the glazed version used a lot in commercial buildings through the 60s in bathrooms and hallways, especially in schools. The unglazed version was usually around 10 in x 10 in but the glazed version usually is the same size as a cinderblock.

JUGHNE

There is a neighbor's house that has, what we call "wall tile", for basement walls.
He had water issues from outside getting into the wall in the west end of the finished basement.
The unfinished utility room with floor drain was in the east end.
I drilled several holes in the bottom tile near the floor drain.
The water would then flow thru the horizontal cores of the wall tile to the floor drain.

This solved 90% of his problems. FWIW

JakeCK

Solid_Fuel_Man said:

Oh, I missed that it was a terracotta foundation. Never have seen that before in my travels. Just, stone, block, pressure treated lumber, and poured concrete. Terracotta is a new one to me. 

I would still avoid polyiso, it doesn't do well with water. 

I don't have an issue with liquid water coming through the walls. Only through the concrete ceiling/front porch floor of the old coal bin. That's getting replaced with the front steps when the collapsed storm sewer is repaired late this spring.

mattmia2

This is the backing for my boiler mounted to the structural clay tile:

JakeCK

mattmia2 said:

This is the backing for my boiler mounted to the structural clay tile:

Yup, that's the stuff. But I have the smooth side on the inside. In the coal bin part of the foundation is single walled and the ribs are exposed in there. My foundation just had a single course down to grade with a brick veneer, and then it widens out to two courses thick at grade. The foundation is seriously like 18" thick down to the footer. 

mattmia2

Mine is only a single block thick and is probably 8" thick or so. I have never seen it without the keys unless it was glazed. It was intended to be plastered or parged. Mine is parged above grade on the outside but just raw block below grade which made spreading waterproofing on it difficult.

JakeCK

I forgot that I had pictures of when the gas co moved my meter a few months ago. I had a fun time digging down and cutting back the old abandoned gas line and patching the foundation. Here is what mine look like, slightly smaller, glazed on one side.

mattmia2

So they're bricks that are glazed on one face or are the cores different than bricks?

Mine are like this:
https://en.wikipedia.org/wiki/Structural_clay_tile#/media/File:Fireproof_construction_for_houses_and_other_buildings_at_moderate_cost.jpg

ChrisJ

They just look like bricks?

JakeCK

They are two core structural terra cotta. They are hollow inside. They are not just bricks.

mlavigne_EK

If you have issues with bulk water, you can always waterproof from the inside, under your polyiso and run that to a drain/sump (see figure 5): https://www.buildingscience.com/documents/building-science-insights-newsletters/bsi-110-keeping-water-out-basements
keep in mind that even if you stop all water from entering your basement from outside, if it is at 60° in the basement and your house is maintained at 75° & 50%RH, any infiltration from your upstairs will be at nearly 80%RH when it cools to basement temperatures. Keeping your basement at 50% RH is going to be difficult at normal basement temperatures (this is equivalent absolute humidity to 35%RH at 75°, or hospital operating room levels of humidity--> $$$).

JefferyLindsey

Larry Weingarten said:

Hi @JakeCK , How about testing by taping down about a foot square of clear plastic. Leave it for a day or so. See what moisture happens under it. If it’s wet, that’s a major source of water. See if you can find a glue to put down vinyl sheet goods.. or maybe tile. That could have a big impact.

Yours, Larry

weather is also effect

JakeCK

mlavigne_EK said:

If you have issues with bulk water, you can always waterproof from the inside, under your polyiso and run that to a drain/sump (see figure 5): https://www.buildingscience.com/documents/building-science-insights-newsletters/bsi-110-keeping-water-out-basements keep in mind that even if you stop all water from entering your basement from outside, if it is at 60° in the basement and your house is maintained at 75° & 50%RH, any infiltration from your upstairs will be at nearly 80%RH when it cools to basement temperatures. Keeping your basement at 50% RH is going to be difficult at normal basement temperatures (this is equivalent absolute humidity to 35%RH at 75°, or hospital operating room levels of humidity--> $$$).

Then it sounds like the trick is to insulate the basement, minimizing condensing surfaces under the dew point and then circulate warm air from upstairs sufficiently to keep the basement around the same temperature?