Building with 'thermal mass'. Are the claims bogus?

[CalG]

Dave

You bring up a different aspect.

That is, the in's and out's of cooling and dehumidifying. (I run a dehumidifier all summer, It's the biggest electrical expense we have!)

There is something to NOT allowing cooler but more humid (night time air) to come into a space that is going to need heat removal a short while later.

Something about the drying of a space taking more energy than cooling it.

Any thoughts on how that plays with thermal storage?

 

[dave1949]

Dave

You bring up a different aspect.

That is, the in's and out's of cooling and dehumidifying. (I run a dehumidifier all summer, It's the biggest electrical expense we have!)

There is something to NOT allowing cooler but more humid (night time air) to come into a space that is going to need heat removal a short while later.

Something about the drying of a space taking more energy than cooling it.

Any thoughts on how that plays with thermal storage?

Not really.

In my case for condensation, I think it comes down to lowering the humidity or warming the cool walls. I have no practical way of warming the walls. ICF walls may be less susceptible to condensation than regular poured concrete, but if true, that ship has sailed. :laughing: Our bermed walls are plaster over concrete.

Lowering the humidity will feel more comfortable and it's absolutely necessary, but I think some cooling would be good too. There is going to be a performance penalty for cooling the thermal mass because it stores a ton of btu's compared to wood frame construction. I don't see any way around that.

If I circulated cool well water in the radiant heat loops, that would cool the slab but only compound the condensation issue, a dehumidifier would be needed in combination with that approach.

What is frustrating is I only need a 2-4 week solution. We haven't tried closing up the house and running a dehumidifier. I think that would get very stuffy without adding an air handler of some sort.

I have four ceiling exhaust fans that vent to the attic space. My theory was in hot weather, we could open windows at night, run the fans to draw in cool air and push it all out the attic vents. That would cool the attic space as well as the house. That doesn't work when it stays warm and humid overnight.

 

[CalG]

Not really.

In my case for condensation, I think it comes down to lowering the humidity or warming the cool walls. I have no practical way of warming the walls. ICF walls may be less susceptible to condensation than regular poured concrete, but if true, that ship has sailed. :laughing: Our bermed walls are plaster over concrete.

If I circulated cool well water in the my radiant heat loops, that would cool the slab but only compound the condensation issue, a dehumidifier would be needed in combination with that approach.

Don't cool the walls

Run the cold well water exposed.

Any humidity that condenses is then "dehumidified". Catch the run off and dispose of it. Iven if the condensate hangs in drops off the pipes, it's still not in the air.

I have a friend not far from here who has a spring running through his cellar. (not uncommon to hit water digging a cellar hole around here)

We set his "cold energy source" up with just over 100 feet of 3/4 inch copper. All at a bit of a slope. with the condensate running down the sloped pipes and dripping into the same outlet as the spring run. The system "appears" to work well. The pipes are dripping all summer, the basement "feels dryer". (he stocks his fire wood there, so dry is improtant!)

Whatever work!

ps

I run the dehumidifier downstairs.

Humid air is lighter than dry air, so there shouldn't be a lot of migration up our open staircase, but I'm sure there is some.

I would never close up the house on those sultry days, It's just not livable!

 

[westcliffe01]

Thats why you need altitude... Low humidity and the temperature drops at night, even in summer... Of course that presents a whole different problem when you want to grow food to eat...

To accomplish de-humidification only requires dropping the temperature of the evaporator to below the indoor dew point. Further cooling beyond that point would be wasteful since it is merely producing cold condensate. If you need an efficient AC/dehumidifier, you need to get one that has a brushless DC motor as opposed to a single speed single phase AC motor with a starter cap. The controller can ramp up the speed of the motor and can also run at the appropriate speed for the conditions instead of simply cycling on and off like a traditional AC. Of course, they cost more to buy, but then you are getting something for the money.

 

[CalG]

Air conditioners are inefficient dehumidifiers. But they help!

 

[2458n]

With heat my house rides right through the outside temperature swings. But you had better start getting it warm three days in advance. Fireplace,baseboard hot water , and electric heat will not make a difference in one day.

 

[dave1949]

Thats why you need altitude... Low humidity and the temperature drops at night, even in summer... Of course that presents a whole different problem when you want to grow food to eat...

To accomplish de-humidification only requires dropping the temperature of the evaporator to below the indoor dew point. Further cooling beyond that point would be wasteful since it is merely producing cold condensate. If you need an efficient AC/dehumidifier, you need to get one that has a brushless DC motor as opposed to a single speed single phase AC motor with a starter cap. The controller can ramp up the speed of the motor and can also run at the appropriate speed for the conditions instead of simply cycling on and off like a traditional AC. Of course, they cost more to buy, but then you are getting something for the money.

Our summer weather the past two years has been odd. We usually get decently cool nights in summer. The past two summers reminded me more of NW Ohio where I grew up. There in Ohio without AC, if you take a shower in the evening, the towel is still wet the next morning.

The garden was happy with the warmth and extended growing season, but lots of folks here are going to AC that never had it before. I'm curious to see what this summer brings.

 

[slowzuki]

Our house is high thermal mass just because we have passive solar and wood heat and we need to soak up / slow down the temp swings inside.

If you have a heat source that you can modulate like oil, propane, gas, etc there is very little point to thermal mass.

Its almost always a better investment to buy insulation.

 

[Paddy]

GalG,

"Air conditioners are inefficient dehumidifiers. But they help!"

I would say I agree if the temp is not the issue. As you know, sizing AC equipment is important. Oversized equipment leaves a damp but cold room. Undersized and it runs all day but can't get the home cool.

Due to our mass, temperature is not the issue. Often, By opening windows at night we can keep it cool.To control the humidity, we have a whole house dehumidifier. It's an AprilAir and can removed 96 pints a day. We set the AC to 75 but set the humidity to 45%. The 75 deg at 45% feels much better to us than 72 deg at 70%.

The whole house dehumidifier is really is nice is when in the Spring and Fall when clearly no heat/cooling is required. The mass is holding the temp in a comfortable range but damp Indiana days get's old. Now is a good example. Our heat has not kicked on for quite some time. But it has been raining alot and the dehumidifier has been cycling a bit.

 

[newbury]

Alchemysa,

We live in a high thermal mass home, it has 100 cu yards of concrete exposed mass on the interior. A total of 400 cu yards including exterior ICF walls. The floors are on steel bar joists with no contact with earth. All the floors are stained concrete. It is a south facing home with a lot of triple pane glass with 32' overhangs. The overhangs were designed to allow max solar during the winter and minimum in the summer.

Each space has in floor radiant heat with a separate t-stat, meaning guest rooms are closed off and not heated. The wood frame interior walls separating these rooms are insulated to insure this is done.

As many have mentioned, the mass acts as a flywheel. So for example, Mid Spring and mid Fall nearly never call for heat or AC. Warm Spring days are offset by cool Spring nights. During the Spring/Fall time frame, there is still 1/2 solar exposure due to the overhangs. Late Spring/early Summer where where it is low 60's at night but high 70's or more, we open some windows during the night. The home stays cool all day after closing.

During the Summer, due to the flywheel effect, the AC often runs late at night. This is fine because it's the coolest time of the day. So you can imagine an AC unit cooling a home to 74 deg with an ambient air of 70-72 deg outside is nearly no load.

During the winter, the heat will not come on if the sun is shinning. But the fact is, Indiana can have some cold gloomy days and requires heat. We leave the heat set constant all Winter, there is almost no way to fight the flywheel by Setback thinking. To give an example of the power of mass during the winter, we had the power go out during an ice storm a few years back. The power was out for 5 days and the temps were in the 'teens. Over that time frame all my neighbors with out wood heat ended up moving out due to frozen water pipes. Our house temp dropped by only 5 deg. It even rose on a sunny day!

At this time we heat with an electric boiler but I would like to install a wood boiler. It would take years for payback though. We do work from the home but other than the window opening/closing for a month in optimum times of Spring/Fall, we do nothing.

Nice house. Also people need to realize that thermal mass does not have to be created by hundreds of cubic yards of concrete, just hundreds of cubic yards of something dense that holds the temperature. Dirt will do.

SWMBO's solution is books.



We also try to keep bookcases against external walls.

I prefer heavy metal tools.