Paging Brad White, Paging Brad White...please go to the nearest

don_185

it sounds like to me you are moving enough air.It also sound like you have your hrv dail in perfectly.

What more could you ask for?

It sound like in Mark case there should have never been a hrv install.If you have to add humidity to a home then surely the house is not as tight as one had assume it was.

[Deleted User]

White telephone...

Brad, I saw your comments about humidity, and it reminded me of a question I need answered. We have a cusstumor who built a home. We and our subs put in a RFH system. One area is largely glass. The home has a GSHP hydronic source, 2nd stage strip resistance forced error back up and humidifier (steamer type). He's trying to set finish materials (teaks walnuts etc), and claims we undersized the steamer for his house because he can't get the RH above 20%. The steamer is rated for a 3000 sq ft home, and his castle is only 1500 sq feet.

He wants to maintain 40% RH for wood stability reasons, and said his pediatrician recommended 55% RH for his new baby.

My thoughts are,

A. If you DO maintain 55% RH, you will have water running down the windows, walls and any where that cold infiltrates into the house, possibly resulting in a black mold issue.

B. I suspect mega infiltration gobbling up the RH, and we will be performing a blower door test next Thursday to confirm or deny this..

C. I can maintain 30 to 40 % RH in my home without much in the way of augmentation humidity, and the wood still wanders.

I forgot to mention that we installed a 150 CFM air to air HRV. Is there a way to calculate the effect of the HRV on RH? BTW, the humidifier has NOT been turned on yet, but will be during the blower door test just to see what affect it has on the whole house ACH.

Thanks for all you do. You're the best (according to Zygat survey:-))

ME

Dave Yates (GrandPAH)_1

It's ALWAYS the mechanical contractors' fault! (GrandPAH)

Funny how it's always our fault! Be sure to check that forced error ductwork for some that splayed open & spewing the humdiditty to the great outdoors. Everything I've read points the finger at 50% as the threshold for most molds. The stacky stuff supposedly needs to be much wetter and likes plumbing leaks.

It's a wonder we don't get blamed for teenagers too!

Ron Gillen

HRV Humidity

Brad can tell you the science. I'll tell you my experience. We've been in our house since last July. I have a 150 cfm Venmar HRV which I ran on low speed full time until about a month ago. RH was down to 29% and oak flooring was starting to open up. Set the HRV to run 20 minutes on 40 off and it's been at 41% ever since.I'd like to move more air but until I figure out the best way to add humidity I'll have to settle for this.

Brad White_9

Is his newborn baby made of teak? Or walnut?

To your questions:

A. You bet, at 55% RH even with double-pane glass, Joe Cocker's "Cry Me a River" will ring in the Owner's head. (Forget Low-E as a factor- it does nothing for actual surface temperature; it is a reflective radiant effect.)

B. I always suspect infiltration.... the HVAC equivalent of "the butler did it".

C. Wood follows the 'Harvard Law of Arts and Sciences': "Under the most tightly controlled conditions of temperature, humidity and other variables, the organism does as it damned well pleases."

If you write me off-line (to spare this forum the tedious process of head scratching, gnashing of teeth and rattling keyboards) and give me the altitude, humidifier output, space volume, assumed infiltration, heat loss, type of glass, outdoor design temperature.... all the good stuff... let me see what I can do for you.

Busy Mardi Gras weekend coming up near us in RI,(et toi!) so it may not be until early next week that I get back to you. But let us begin...

If the outcome has general interest, we can post the results or at least my assumptions

Thanks for thinking of me!

Brad

Brad White_9

65% ambient RH

is what we consider a threshhold for mold growth at least from an archivists perspective. At that RH, the fungi (as opposed to Fun Guy which is you, Dave), can draw the moisture it needs right from the air itself... So we keep 60% as an upper limit when so controlling....

Actually, the teenager part? Making bedrooms comfortable and cozy does have that effect with a 13 year latency period...

don_185

You bet

You bet it has interest.I would think it would be another
tool in the tool bag for all.

Nothing like discussing the dew point and psychrometrics in general.

Brad White_9

Mass Flow

(The flow of air and associated moisture as opposed to the exodus from our state.)

The science is psychrometrics, the study and measurement of energy transfered via air.

In short, you are moving so much air at a certain specific humidity (lower) into a space with higher humidity and it leaves after absorbing what it picks up. Similar to airflow and temperature but this is dealing with the latent or moisture-related side.

Depending on temperature and elevation, a pound of air has a volume of between 11 and 14 cubic feet in volume at sea level at least. At 70F it is about 13.5 CF/lb.

Each pound of air at a given temperature can hold so many grains of moisture ("grains per pound"). There are 7,000 of those suckers in a pound to give you an idea of scale here.

At sea level, saturated air (100% RH) at zero degrees has 5.51 grains per pound.

When that pound of air sneaks into your house as a humidity burglar, the resulting RH of the air it replaces drops to 5.1% RH- same amount of humidity, but what a dry sponge it is, that air. Just by raising the temperature to 70 degrees and without dropping off any humidity, the RH plummets.

You can see how RH outside means bupkes. It is all "absolute humidity", the grains per pound being the terms I use.

Now, if the indoor air was kept at 30% RH (70 degrees), the grains per pound would be 32.66 if steady-state. The delta-grains per pound, indoor to outdoor, is 27.15 IF the outside air is saturated- foggy. As if that happens.

We usually assume zero grains for winter outside air because, well, the math is easy...

So... that 150 CFM of cold yet saturated air being forced in via the HRV? That is 150/11.6 CF per pound or 12.93 call it 13 pounds of air per minute. Times 60 minutes that is 780 pounds per hour. Each pound carries with it 27.15 grains so you are losing 780 x 27.15 = 21,177 grains per hour. Divide by 7,000 grains per pound and that is about 3 lbs. of moisture per hour. 1.5 Quarts.

This does not even count the moisture driven by vapor pressure but that is at most about 10-15% of the infiltration number, often less in a tight modern house. It also does not account for infiltration. If a 2,000 SF house with 9 foot ceilings (18,000 CF volume) and 0.50 ACH, that is another 150 cfm or 3 lbs. right there...

G.Kaske_2

wandering wood and babies

Mark most fine furniture is made with moisture content of 12% bench mark to keep its shape. Doubt you will get that with hardwwod floors unless in a controlled kiln.

Best he can do is let the flooring aclimate to its installed enviroment. What ever happens from the point after that was going to happen any way. Humidity levels fluctuate alot from spring to winter in a home usually.

So unless the wood is sealed on all sides it will absorb or disipate moisture always trying to equalize with its enviroment.


Babies....It has been noted that keeping the realitive humidity in the 55% range reduces respitory related difficulties in new borns, and adults alike. problem is as been noted by everyone is it brings havoke to the home in the winter. I just finally got my windows to quit crying when the humidity got down around 25%.

So what are you suppose to do about it? Get the baby a humidifier, and keep the humid region localized to the sleeping quarters?

I doubt you can have the best of both worlds in this case. The house, the wood floors, and the baby have to meet on common ground.

Just a wood ticks perspective

Gordy

J.C.A._3

G.Kaske....

As an outside observer, What would YOU consider a "fair time" for the varieties of wood used for flooring, as being aclimated?

I've run round the block with Floor Guys about this time, and time again. I never win the battle, but the homeowner looks to ME when the stuffs got gaps big enough to hide said babies in!

What say you? Chris

Brad White

My dad

(a master cabinetmaker and, well, master just about anything) always told me two to three weeks.

It is not the actual humidity but the rate of change. (If wood could not tolerate dryness, I recently told the architect of a music building, there would be no pianos in Arizona.)

J.C.A._3

Thanks Brad.

I tell the "contractors" that will be putting wood over my RFH stuff, to give me at least 3 weeks...preferably 30 days or better. They give me that "deer in the headlights look" and wonder where I came up with THAT.

The first wood floor w/ radiant I did, the wood sat for almost a month and there are NO problems. A couple more that didn't sit quite as long...ended up cupping and warping for a couple different reasons.

1 was the floor guy putting a nail in the tubing....That one had some warping in the entrance to the kitchen (OOPS! it was replaced with tile AFTER a ripout of the flooring, tubing and Climate Panel that was soaked and replaced!) and the worst was the 600 sq. ft. kitchen with "wide pine" that you can fit your fist in the gaps because the wood sat for about 1 and 1/2 weeks.

Do I look that dumb? I TRIED to tell them, but I'm just a heat guy...what do I know from wood?

Life is short...Play HARD! Chris

Gordy

wood aclimation

Brad beat me to it, and usual he is right on. Fact of the matter is when time is money know one wants to listen right, or wrong.. To bad lotta nice wood goes to hell. Really to bad you guys get the blame.

Gordy

Gordy

Different factors

JCA one big key to a tight wood floor besides wood aclimation is the width of the flooring. Narrower the better. Thats why you never see gymnasiums with wide boards.

Gordy

jp_2

also helps

to unbundle the wood and spread it out.

Gordy

Yes

Yes that is a must. If you guys are looking for numbers.
For installation
The house should be between 60 and 80 degrees
RH between 30 and 50 percent.
Wood flooring should be with in plus or minus 4% of RH in the dwelling a good wood floor guy packs a moisture meter.
Gordy

Weezbo

Brad, Mark, Dave...

take a look on Wisdom associates web site...

they have some very clear picture of high RH in a home...

Tombig_2

Brad

We are lucky indeed to have you hanging around The Wall. Let's drift back to your humble beginnings......

[Deleted User]

WOW...

Theres a lot more to this than I expected. For the benefit of all concerned, I'm going to have my project manager (Jim French) respond to your request for information here on the Wall. And if you don't mind, I think it would be prudent to do it out here in the open for all to learn and benefit from. I really appreciate your valid input Brad. I owe you numeorus adult beverages.

If it works out that were wrong, then we fix it at our expense and learn an expensive lesson and move on down the road. This is new, uncharted territory for me. But I ain't scared :-)

Thanks again for all your time Brad. You and the Bean (Robert Bean) are major assets to this industry.

ME

Brad White

Now THAT

is comedy! I loved it. Thanks for the compliment!

True story- When I was about seven, I appeared on a Boston children's show, WBZ-TV's "Rex Trailer's Boomtown" (familiar to all Bostonians growing up in the 50's and 60's).

The contest was on where every kid chosen had a box of balloons and on the word "Go" you had a minute to pick up all the balloons you could. Most balloons wins. Those were the rules.

At "go!", I simply picked up the box with the balloons in it.

They disqualified me for "cheating". Rex was never the same in my eyes after that. His horse, "Goldrush" made a spontaneous contribution to the nitrogen cycle in disgust at the decision.

Brad White

Wow indeed, Mark...

I am humbled to be placed in the same sentence with Mr. Bean and by you yourself no less. Thank you.

Yes, by all means have Jim post it here, either in this thread or start another. If you have blower door test data, more concrete information in general, the better.

The more tedious stuff we can cover off-line as well. Have Jim give me a heads-up off-line that it is coming at least, in case I miss it. Happy to help!

Brad

Tombig_2

Balloons

I see you were just as clever at age seven. They should have given you SOMETHING for thinking on your feet so well at such a tender age. At least recruited you into the CIA.

Oddly enough my sister sent me the math funnies that very day. Here's a couple more. Brought back painful memories of physics class.