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Humidity control in tight houses

This building is mentioned in the book Sun, Wind, and Light by Mark DeKay and GZ Brown. Not sure if it applicable, and they are doing this 'labyrinth' to cool a data center. But wonder how having a non perforated pipe at the slab edge perimeter blowing or finding a way to get the air to circulate naturally pulling that cool air out of the concrete into the air in the summer also bringing the concrete away from the dew point? I have a similar condition at my home office. It is in the lower level on a slab against the exterior wall. It is not insulated. My legs ache with the cold that comes off of that concrete.
 
Radiant cooling might work well in the desert Southwest, but it could be a disaster in the humid Southeast without very tight control of the dewpoint.
 
So where I hang my hat is climate zone 4, almost as many cooling degree days as heating degree days so what i say comes from a location where a vapor barrier could be two coats of paint on the drywall...

As previously mentioned an erv or hrv really doesn't dehumidify well.
What might work well 10 months of the year in Main or Vermont might fail for the times mentioned by the OP.

Has anyone tried straight up exhaust only for those times?
A fallacy is exhaust only wont work on a tight home. I have successfully measured energy star labled exhaust fans producing 120+ cfm in sub 1000 sq ft houses at well under 2ach50. Many, many times and for 10+ years. If the fan is exhausting air, the air is coming in. The only reason NOT to rely on this is if you have radon issues. Thats the one and only reason not to ever use exhaust only in my book.

Im also not sure of the daily range for the area in question. I can certainly see warm / hot humid days followed by cool evenings being an issue. The humidity in the home has to follow the laws of physics and a physcrometric chart can simply tell you at what temperature what RH will condensation occur. The trick would be to lower that RH before the dew point is reached. A lower RH requires a colder surface to condensate on.
With tile floors damp to the touch, thats a tad late in getting ahead of the curve.

So remove the moisture first. Again i dont know the location, would be curious to look up what the daily range is ( biggest spread or delta between daytime and nighttime temperature) so cant say what I believe is the correct path.
Or
Raise the temperature of the floor above its condensation point.
That said, i again dont have enough data to say whats the best approach.
I would recommend during a worst case situation, a few strips of painters tape on the floor in question (few small areas) and measure the floors surface temperature with an infrared thermometer. The tape is needed to "normalize" (some surfaces do not emit heat in the way an infrared thermometer reads and can give bad readings) the emissivity for an accurate reading. Then an accurate digital rh meter to know exactly what the indoor air moisture content is. Lastly an accurate indoor and outdoor temperature. At least with this info and a physcrometric chart you can tell how far you need to go to correct this worst case scenario.

While all of this is new and ground breaking for many, the field of building science isnt and has all of these items already solved a hundred times over. The true issue is its complexity and the knowledge of your "expert".
This is not a dig. This is simply a reaffirmation of the complexity of high performance homes.

Lastly, what i have found to be true in almost all if not all touble situations is what I call big ticket items overlooked or not accounted for at all being the true cause of any issues.
1) grading. Is the land sloped away so no moisture is collected within 5-10 feet of the building (soil conditions differ)
2) is the ventilation actually producing whats been designed?
Is it on a timer, running 24x7, actually vented correctly etc....
3) is the thermal control layer continous?
4) is there a source of excessive indoor moisture? unvented gas fired equipment, 10,000 gallon fish tank, hundreds of plants, indoor pool or spa, bathroom exhaust fans not terminated to the exterior, daisy changed bath exhaust without back flow dampers.
5) walls without a vapor profile (reservoir)
6) new construction and poured concrete can take a year to loose most of its moisture, causing many of these issues. Dehumidifier in crawl spaces and basements with condensation pumps are a must in my area. After the 1st year almost all of these moisture issues dissappear...
 
So it pays to actually read the OP completely. My mistake by skimming it. My apologies to all.. The answer was mentioned, but to reinforce it, having a cooling system that is over-sized, not running long enough to dehumidify on your design day is 100% the issue.
90-115% of the load is manual s for cooling. If you see 90% and worry that it cant meet your forgetting duty cycle. So if the manual J said you needed 2.25 tons, 2 would actually work. Hows that you might ask, well a properly sized system would probably only run 75% of the time on a design day and have 25% of extra capacity for excursions above design. An over-sized system will get the houses temperature down quickly but won't be able to dehumidify the air. It takes many passes over the coil to remove moisture, and a saturated coil cant cool properly.
Once you open the windows and let moist air in the colder surfaces will surley condensate. And once the windows are open, the issue has nothing to do with having a tight house.
So you don't believe the manual J, or don't believe it was rigorous enough, get multistage equipment sized correctly so it runs longer on its low speed sensors for proper dehumidification. Multistage equipment was actually designed to manage moisture issues in homes when the system was sized correctly but needed higher latent capabilities. May be one in every 5000 houses fall into this category. Manual J while the most accurate method commonly available isn't fool proof. That said, it works nearly 100% of the time on every house, in every state, every country there is. Still folks don't trust it.
Many miss purpose Multistage equipment successfully. The trick is to not over-size it so much that the medium or high output settings are never used. Shoot for the 115% if needed and always have dehumidifing cool air circulating.
 
bcoop said:
I paid for a professional engineer to design the system and did not rely on the contractor or their supplier.
Click to expand...
Yes but did the contractor follow the design or maybe he got a great deal on a 3 ton unit the supplier was wanting to unload.

Ask your engineer who designed the system to see if what you have is what he designed.
 
Ah, the joys of modern construction, where we've traded the quaint quirks of yesteryear's homes for the sterile efficiency of today’s airtight fortresses. Your tale of tightly sealed houses and their accompanying humidity woes strikes a familiar chord, one that resonates with the many abodes I’ve owned across the globe.

You see, my friends, I've had the pleasure of residing in some truly venerable homes. From the charmingly crooked cottages of the English countryside to the stately, drafty manors in the heart of Europe, each one was a character in its own right. These homes, some standing for centuries, had one thing in common—they breathed. Yes, they were leaky, and yes, they let the outside air in, but therein lay their genius.

In their infinite wisdom, the builders of old allowed these houses to interact with their environment, to let the air flow naturally. The drafts we often cursed in winter were the very breaths that kept these homes alive, preventing the damp and rot that could spell an early demise.

Contrast this with our modern marvels—airtight, energy-efficient, and insulated to within an inch of their lives. We’ve created perfectly sealed boxes, inadvertently setting the stage for high humidity and condensation woes. A home that cannot breathe is a home on borrowed time, at risk of fostering unhealthy conditions for its occupants.

Picture, if you will, a grand old lady, her windows ajar, curtains billowing as the breeze dances through. Now envision her sealed shut, stifling, unable to breathe. This is what we risk with our airtight constructions.

So, let us ponder this: in our quest for efficiency, are we dooming our homes to an early death? Or worse, are we creating environments that compromise the health of those who dwell within?

As a seasoned traveler through time and space, I advocate for a balanced approach. Let our homes breathe, let them interact with their environment. Perhaps, a little less focus on sealing every crack and a bit more on ensuring proper ventilation might be the key. After all, it's the breath of life that keeps us all going.

In closing, let us remember the wisdom of the past as we build the future. Our homes, much like us, need to breathe.

Yours in timeless charm,
Raymond
 
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