EcoRenovator  

Go Back   EcoRenovator > Improvements > Renovations & New Construction
Advanced Search
 


Blog 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 04-20-12, 11:10 PM   #21
Drake
DIY Guy
 
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts
Default

I didn't intend to slander earth sheltering only point out it is being done and that detail to moisture control is very important, not inexpensive and doesn't fit every location. Humid summer areas challenge the design. Some of the best performing ones today are built with PWF lumber or ICF's.

Drake is offline   Reply With Quote
Old 04-21-12, 09:39 PM   #22
S-F
You Ain't Me
 
S-F's Avatar
 
Join Date: Nov 2009
Location: Northampton MA
Posts: 662
Thanks: 6
Thanked 70 Times in 58 Posts
Default

Yeah, below grade moisture management is a b@&*c. I have to run a dehumidifier in the summer to keep my house safe. Insulation next to below grade masonry is a temperamental situation. It might be ok if you had R 40 on the outside of every concrete surface with proper capillary barriers and so forth. But at that rate you are in the same boat as people super insulating above grade. I'd love to live in such a house but I think it's a lot cheaper and easier to build a house on grade or retrofit an existing one. The retrofit is the easiest and most effective option but maybe not the cheapest.
__________________
My project:


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


Chipping away on a daily basis.

Quote:
You know you're an ecorenovator if anything worth insulating is worth superinsulating.
Quote:
S-F: "What happens when you slam the door on a really tight house? Do the basement windows blow out?"

Green Building Guru: "You can't slam the door on a really tight house. You have to work to pull it shut."
S-F is offline   Reply With Quote
Old 04-26-12, 09:09 PM   #23
JRMichler
Apprentice EcoRenovator
 
Join Date: Apr 2012
Location: Phillips, WI
Posts: 102
Thanks: 8
Thanked 24 Times in 20 Posts
Default

Humidity control is necessary in any well insulated house located in a humid climate. We learned this when we built our house in 2002. When the outside temperature rose into the 80's or 90's and the dew point into the 70's, the inside temperature would stay in the low 70's and the inside turned into a swamp. We had a choice - get a dehumidifier or turn on the heat. We got the dehumidifier.

Above grade or below makes no difference - it's the indoor relative humidity. Mold happens when indoor relative humidity gets over 60%.

Last edited by JRMichler; 04-26-12 at 09:12 PM..
JRMichler is offline   Reply With Quote
Old 04-27-12, 12:38 PM   #24
MN Renovator
Less usage=Cheaper bills
 
MN Renovator's Avatar
 
Join Date: Nov 2010
Location: Minneapolis, MN
Posts: 930
Thanks: 41
Thanked 113 Times in 87 Posts
Default

Your air conditioner is a dehumidifier. In Minnesota we got dew points well above the indoor temperature but as long as the air conditioner was used to bring the house down to a reasonable temperature, the humidity was plenty low. I managed to pull humidity down to 25% during the hottest weeks of the year and most weeks I'd have it in the low to mid 30's. If I let it get warmer, aka less use of the air conditioner I would have humidity in the 40's. I aimed to keep the dew point of the house below 50 degrees.

The success of an air conditioner dehumidifying your house is dependent on long cycle times, which becomes difficult when an HVAC contractor oversizes the A/C. If the blower speed is too high and the coil isn't cold enough to dehumidify the air, you have the same problem. Also if you don't have a well sealed house, you are letting humidity in, which seems to be the most likely scenario for you if you are having this problem but it is probably a combination of those issues.

The issue with dehumidifiers is that they essentially are an air conditioner with both the indoor and outdoor components inside, they leave you with a net gain of heat while drawing off moisture to a catch bucket or a drain. I made the mistake last year after reading on the hvac-talk forums that dehumidifiers were more efficient at removing humidity so I monitored my humidity and kept it at 40% but the dehum. never shut off to keep it there and burned 400watts to no end. The house was warm but the humidity level kept it comfortable enough. I ended up with the highest electric bill. I dehumidified my house using the air conditioner the following month when it was hotter and my electric bill was actually lower.

In the summer if you have issues with your humidity being that high, you should try letting the house get a little bit warm and try running your air conditioner in one cycle 4-8 hours long and tell me what happens to your humidity level. Running a long cycle will keep the a/c running its most efficient and remove the most humidity. These 30 minute cycles that some people have get rid of very little humidity.

This summer I'll be trying to use a 10.7 EER(energy star) 5k BTU/hr window A/C which is a higher EER than my current air conditioner's SEER(1986 unit) and will be in my bedroom where I want the most comfort, mostly for sleeping. If it can't keep up cooling the whole house, I will close the bedroom door and when it is overcooling the bedroom I'll open the door. If needed I'll cycle the furnace blower for a bit to suck the air around or use a few of my box fans. I got a good knack for working the 23k whole house unit last year to keep the humidity down and expect this unit if setup and used properly will do better and be cheaper.
MN Renovator is offline   Reply With Quote
Old 04-27-12, 04:13 PM   #25
Drake
DIY Guy
 
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts
Default

You are not wrong that A/C dehumidifies but ideally I space that doesn't need cooling is the goal. A/C's do offer the advantage of keeping the heat removed outside of space over dehumidifiers. Is one more energy efficient?
Drake is offline   Reply With Quote
Old 04-27-12, 09:54 PM   #26
JRMichler
Apprentice EcoRenovator
 
Join Date: Apr 2012
Location: Phillips, WI
Posts: 102
Thanks: 8
Thanked 24 Times in 20 Posts
Default

An energy efficient house needs very little cooling. Our house has a one ton AC. The house also has zero shade.

During a heat wave where the daytime temperature stayed above 100 deg F all day, the AC only ran 58% of the time to maintain 79 F inside. That was not enough running to fully control the indoor humidity.

More typical summer weather has daytime temperatures in the 80's with dewpoints in the 60's and low 70's. Typically, when the outside temperature rises into the 80's, it's several days before we turn on the AC. Keeping the indoor dewpoint down below 60 deg F requires a dehumidifier.

Last edited by JRMichler; 04-27-12 at 09:57 PM..
JRMichler is offline   Reply With Quote
Old 04-27-12, 10:03 PM   #27
MN Renovator
Less usage=Cheaper bills
 
MN Renovator's Avatar
 
Join Date: Nov 2010
Location: Minneapolis, MN
Posts: 930
Thanks: 41
Thanked 113 Times in 87 Posts
Default

They go make dehumidifiers that also have ventilation capability. It seems that type is also the most efficient dehumidifier, two birds with one stone there.

MN Renovator is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 03:26 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design