ReplyVery interesting. Looking forward to more info as things progress.
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Sponsor & Professional Member*
Humidity Research- This will be interesting. I have started my research early. I have be trying to data log my home looking at humidity control. The first thing that went wrong was my water heater flooded my basement bedroom. Posting a week of drying out the basement with 2 90 pint dehus and couple box fans. I am just getting a little cooling load in WI. Took 9 days to dryout the carpet. More to follow for those that are interested. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Regular Guest
Very interesting. Looking forward to more info as things progress.
.
Regular Guest
Good study...
Are you the principle or a participant ?
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I know the principles but I am not participant. I also use onset data loggers also. I am attaching the afternoon of the greatest amount of cooling I have had so far this year. The VS fan is "on" mode. This demonstrates the negative effect of air drying the cooling coil at the end of cooling cycle. This afternoon of cooling removed 12 lbs. of moisture with a/c. Following the end of the cooling cycle, the indoor %RH rises about 5%RH. I only had 4 cooling cycles for the day, about 6 hours of cooling. More to follow. Regards TBOriginally Posted by adamk
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Professional Member*
Interesting stuff, TB. Thanks for the link and data.
This past Saturday, I observed 101 degrees and 20% relative humidity outside my house for the first time this year. Interior conditions held 74-76 ^F, humidity 42-46%, as unit cycled approx. 20 minutes on, 6 to 8 minutes off. For us these outdoor conditions were exceptionally dry, given the dewpoint of 52 degrees...what might translate to a milder, more humid day in Phoenix, AZ!
Then, to demonstrate the variability of our weather, today it is mostly overcast, 88 degrees with an outdoor dew point of 73 degrees. When I got home yesterday, these same weather conditions were more or less in place. The house interior environment was still quite managable at mid-40's humidity and temps 73-76 as unit cycled with approx. 10 on/10 off run times, + or - a minute or so.
Admittedly I'd like much more hard data to form opinions for my observations, but at this point it appears a house that has undergone installation of radiant barrier, increased attic insulation, efforts to seal penetrations between attic and interior, and gasketing of wall outlets and switches, equates to a house that can cycle its a/c system on a near design day (for us it is 100 degrees/74 wet bulb) and not only meet interior design targets (75^F @ 50%), but do better than the targets, especially on the humidity side. I wish to do more extensive observation of temperature gradiant throughout the house, but a walk-around with an accurate digital pyschrometer revealed minimal temperature swings from room to room.
So, all of this has bolstered my increasing understanding that house structure and a/c system are steadfastly dovetailed, and to achieve excellent performance, both the structural envelope and a/c system MUST work as a cohesive unit, a team. The traditional approach is to throw a lot of equipment at what amounts to a poor thermal envelope vs. striking a balance between envelope that shelters adequately from extremes in climate, and a/c system that controls climate and also provides adequate fresh air ventilation.
IOW, it's possible I'm now a tad oversized in capacity, but I'm comfortable. Our last electric bill was under 200 @ 17 cents/KW, for an 1,800 square foot single story mid-century modern house built in 1959, with original single pane aluminum frame windows and two sliding glass doors. The mid-century modern style means it has a bit more glass than perhaps a traditional style house of the same square footage.
So...in a nutshell, cutting the heat load from attic to house, sealing between house and attic, and providing adequate shading of all glass surfaces as much as possible (house has three foot overhang all the way around, house is oriented broadsides facing southwest and northeast) pays dividends at the electric meter, AND keeps a big guy like me comfortable (wife freezes when I'm home and t-stat is set at 75).
Professional Member*
The manufacturers of equipment have dealt with the issues for years. Run the blower after the system reaches set-point? Why? IAQ is one main reason. Temperature rise around a stationary occupant is another as the body warms the air enveloping it. So how do you continue to provide good IAQ with the blower running and still keep the place from re-humidifying when the set point is reached? The manufacturers answer is multi-stage units. Instead of reaching set-point on 2nd stage and cycling off, they cycle back to 1st stage, which keeps dehumidifying and runs the IAQ products and slows the temp rise back to 2nd stage operation. It also lowers the electrical consumption. I replaced my old 10-SEER (still operating, mind you) AC system last fall with a 18-SEER, 2-Stage HP. Both sytems operated the blower 24/7/365 for IAQ for my wife's allergies. Tracking the electrical shows a decrease of 34% in useage and I'm now heating my house whenever the OAT is 35 or higher using the HP. The humidity level is substantially lower in the house than it ever was before with the 2-stage. That's the total solution and ends the debate about operating the blower after the sytem reaches set-point. With 2-stage, it rarely does.
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!
Regular Guest
TB, perhaps this is redundant to what you have posted before but... do you directly measure condensate or is it calculated from measurements of air temperature and humidity? Just wondering about the methodology.
Best wishes -- Pstu
Sponsor & Professional Member*
I am catching the condensate from the dehu and the a/c. I am tracking the electrical also. Better data coming as the a/c load increases. Clearly grossly oversized systems should not operate the fan continuously in a partially load condition. More stuff is a couple days. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Regular Guest
Somehow your method seems superior to me. Maybe it is just that a person doesn't have to be smart or educated to understand a container measured in pints of water. I like things that are simple and obvious.
The alternative using psychrometrics and math, might be equally good but I cannot help wondering if the equations leave out something important. Any comments on that? One way or the other, I sure am glad to see studies of humidity removal in "regular" houses so we can better understand what goes on.
Best wishes -- Pstu
Professional Member*
For what TB is doing, his method is fine. If I were to do performance testing on a system, and could only observe the system's operation by one run-through of data gathering (such as during a service call or during an energy audit), the psychro chart and formulas get the job done, provided recording moisture removal performance is a point on one's performance checklist (which it should be).
Humidity removal in "regular" homes ain't rocket surgery.
Or...the house may be architecturally difficult to manage the interior environment...giraffe barn high ceilings combined with poor supply and return register placement can inadequately stir the air in such a house, causing zones of stagnation where temperature and humidity could increase.
It may not be rocket science, but it IS a science...building science coupled to psychrometric control (HVAC). Like Carnak has posted elsewhere, we're a bit slow here in good ol' USA to come to the building science dinner table, but we're now collectively being urged to take a seat and pick up a fork. Personally I find what's on the table more appetizing than the utility bill that arrives each month.
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My objective in monitoring my home by data logging is to determine the amount of moisture removal needed to maintain <50%RH. First is a series with varible outdoor conditions and natural infiltration. I am monitoring the air flow through a 30"X1" cracked window. The fresh air flow is very low during lite winds. This indicates that wind sheltered homes get very little fresh air during the summer compared to winter stack effect. Next is to provide 50 cfm of fresh make-up air through a dehumidifier with varible weather conditions. Make-up air ventilation slows infiltration by 50% of the make-up rate. In other words, if a home is leaking at a 50 cfm rate(in/out), mechanical ventilation affect the natural leakage. 50 cfm of make-up air changes the natural leakage to 25 cfm infiltration and 75 cfm of exfiltration.
Also VS fan "on" and "auto" effect on the moisture load in the home is of interest.
The last point is setting up the t-stat when the home is not occupied during the day as much as possible.
The t-stat set-up limitation is possibly the a/c's ability to reduce the homes temperature in two hours. I have noticed that t-stat set-down provides a significant of length a/c operation. That is great for moisture removal by the a/c especially over-sized a/cs.
We will get to +90^F, +75^F dew point today. I will post data. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Professional Member
I have about a one year head start on this program.
It is a good study, but an opportunity is being wasted to see the whole picture.
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This the last couple days after over-drying the basement to dry a wet carpet. I am raising the basement %RH from <40%RH to 50%RH. I will include the lbs. of moisture removed when the home stabilizes. The a/c is not over-sized for sure. With the t-stat setup during the day, the run times are long. The VS blower "on" slow incorpates basement cooling in the flywheel. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Sponsor & Professional Member*
Updated graph on WI home. Raised the dehu setting and incorporating the dehu on/off along with basement %RH. Tring to get the a/c more involved with humidity control of the home. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Professional Member
Maybe just mark the time axis once a day like midnight or every couple hours on the hour
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Here is a comparison of natural infiltration with a 30" window cracked 1" compared to 50 cfm of fresh air via a ventilating dehu with the dehu "off". The next couple days have the dehu set down to 45%RH and fresh air on. The impact is clear on the mainfloor, low %RH. The basement was wet with 50 cfm of fresh air and dehu "off". The 50 cfm of fresh air changed the freshness of the home. Perfect conditions with fresh air on and 45% RH. This week providing 50 cfm of fresh air during occupancy. 4:00 PM to 6:00 AM. VS fan "on" with ac set-up to 80^F, 76^F at 4:00 PM, 75^F at 9:30 PM. Raising the %RH setting on the dehu to 53%RH in the basement. The a/c control always reads the %RH 5% less than any of the data loggers. More to follow. Regards TB
Last edited by teddy bear; 07-21-2008 at 07:07 PM. Reason: attaching graph
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Sponsor & Professional Member*
Trying to attach this graph to the previous post. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Sponsor & Professional Member*
One more shot at the graph. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Sponsor & Professional Member*
Increased the make-up air from 38 cfm to 58 cfm of fresh make-up from 4:00 pm to 6:00 am through the dehu. The dehu operates only during these hours. Cooling load is declining cycling more. VS fan "on" mode. Looking at changing to ""auto" during afternoon/evening hours. Also looking at delaying fresh air ventilation start or different timer cycle. Home air much better with mechanical fresh air as a opposed to natural ventilation through air leaks + 1" x 30" cracked window. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Sponsor & Professional Member*
July 22-23 is cooler, drier weather. Very little cooling load. The end of this day, the outdoor dew point is close to the desired indoor dew point. The dehu is removing 2-3 lbs. of moisture per hour and indoor dew point is not dropping. This may indicate that much of the 2-3 lbs. per hour of moisture is the moisture load from the structure and occupants. We will know more with lower outdoor dew points this fall. Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
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