Dehumidifer

OK...so in my last post i talked about how I turned my vented crawl space to an unvented crawl space.  Overall, it isn't doing too bad.  Humidity is around 50% inside the house, while I have the crawl space dehumidifer set to 60%...although the wireless sensor I have in there says its around 55%.  Whatever...

Well...one thing has been bothering me, which is the amount of time, the dehumidifier runs.  Where the heck is the wet air coming from?  See the pic from TED below:

This is minute data...and you can see the small bumps in power usage.  Looking further, it appears the dehumidifer is turning on roughly 6-7x/hour.  When it runs...it runs for roughly 2-3 minutes.  Doing the math...24 hrs/day x 7ops/hr x 3 min/ops = 504 minutes per day of operation.  504 minutes = 8.4 hrs.  Why is this thing running for 8.4 hours? 

I went down into the crawl space and checked the door...and its sealed pretty tightly.  I checked all the vents and all were well sealed...except 2, which I added more caulking to yesterday.  But...no substantial change in operation.  I also checked the plastic and didn't find anything. 

Here's my theories:

1)  There's some holes at the end of the crawl space that appear to be ports to look at the steel beams under my garage workshop.  Some moisture could be coming from there...

2) Some moisture is coming from the house.  However...I'm holding 50-55% RH inside the house according to the inside thermostats...so it shouldn't be running unless the RH inside the house gets higher.  This could be a factor...but I doubt its contributing.

3)  The crawl space is not 100% sealed.  I'm sure there's some, but I would think that there isn't enough humidity entering to account for 2.8 pints/day (That's 50 pints/day capacity of the dehumidifier x 24/8.4).

4)  The dehumidifer humidistat is too sensitive/not all that great.  This wouldn't surprise me one bit...especially since I have the unit set to maintain 60% RH and the wireless sensor nearby is showing 55% RH.  I could setup the dehumidifer to only operate for X hrs/day (I think its limited to 3, 6, 8, or 12 hrs.)  I may try that to see how it works.  I'll try it low...like 3 hrs to see how well it does.  Generally, humidity is highest in the morning...so I'll have it run then. 

So...overall, I think I'll buy some spray in foam to close those holes/ports at the end of the crawl space.  Then I'll setup the demudifier to only operate for a set amount of time.  And then I'll monitor some more.

Initial Energy Savings! 30-40%!

Probably for the first time....I was super excited to get my Duke Energy bill.  This is one of the first bills to really show all my energy efficiency work.  What was the results?

Last month I used 526 kWh.  That's lowest we've had since moving in and equals 17.53 kWh/d.  That's even lower than the previous month (593 kWh) when we didn't use the HVAC at all.

How are we doing compared to last year?

March 2010 vs 2011:  34% less <---some heating until late in the month
April 2010 vs 2011:  4% less <---didn't use HVAC at all
May 2010 vs 2011:  41% less <---cooling started late in the month

Just awesome!  I'm thrilled...it's showing all that work is cashing in.

I also decided to compare my energy usage between this home (built 1986, 2700 sf) versus our old townhome (built 2005, 1300 sf).  Note for the "old" townhome I had to convert natural gas usage to electricity equivalent because both hot water heater and cooking used natural gas.  It's an easy conversion...if you want to know...ask.    OK here's the total energy consumption between the two places:

Feb 2011 vs Feb 2009: 26% less
Mar 2011 vs Mar 2009: 39% less
Apr 2011 vs Apr 2009:  22% less
May 2011 vs May 2009:  26% less

How awesome is that?  Our older, larger home is more energy efficiency than the newer, smaller, townhome.  Frickin' awesome.  I'm excited to see what the next bill shows...until July!!!

Pic of finished crawl space

Here's a pic of the finished crawl space.  Nice, huh?  I put down unused shingles at the entrance and around the hvac equipment to minimize damage during routine maintenance.

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Crawl Space Conditioning

Wow...it's been a while since I last posted.  But, things have been slow...until recently when I discovered lots of moisure in my crawl space.  Some background:

In the hot and humid south, moisture control is important in the crawl space to insure you don't allow mold to grow or provide ideal conditions for insects which can damage the underfloor joists for the house.   Old technology to control moisture was to put plastic on the ground (aka a vapor barrier) which would stop water for coming out of the soil.  It would also include putting in vents to "ventilate" the crawl spaces thereby removing moisture.  However...recent studies (Example:  http://www.smartvent.net/docs/crawlspacestudy.pdf or http://www.rlcengineering.com/csfallacies.htm) have shown that while some moisture is from the earth...the majority of it generally comes from the humidity in the air.   Note that folks are making a living off of fixing crawl spaces...for example:  http://www.dryprosystems.com/crawl-space-repair/vapor-barrier.html

Well...so far this summer has seen some very hot and humid days.  In the past week temperatures have been in the lower-mid 90s with the humidity between 65 and 87%.  Well...when those hot temperatures and the high humidity, when the air enters the crawl space, it can reach the dew point and begin codensation.  That's what I found in my crawl space.  I had been monitoring my crawl space using a wireless weather station with the transmitter located in the crawl space.  I thought it was fantastic that my crawl space had 20% humidity until I started getting suspicous during the past couple weeks 80+% humidity days.  So I checked the meter and the humidstat was broken.  I bought another weather station (Walmart - $15) and saw the truth...my crawl space had humidities in the 70-80% range.  That's bad.  And when I checked out the crawl space for mold, I didn't see any (good...probably because last year I went around and used a moldicide when I found some during a energy audit).  But I did find condenation all over what was left of my old vapor barrier (which was in various pieces...torn a lot...barely covering the sand floor). 

I had gotten an estimate in the past to encapsulate the crawl space and wow was it expensive:  $2800 for a 20Mil liner plus dehumidifer.  And over $7,000 for the full encapsulation which includes spray foam insulation on the crawl space walls. 

Screw that...I'm doing it myself.  Here's the method I used:  http://www.dom.com/about/conservation/pdf/crawlspaces.pdf  (Unvented crawl space).  Note: my crawl space is about 1300 sf and varies from about 4.5-ft in height to about 3 in height.  Not too bad. Here's a very  old pic when we moved in that shows the hot water heater (which now has insulation on it and all the hot water pipes have insulation as well):

See how it looks like crap in there?

So, on Saturday @ 6am,  I began 15 hours of fun in the crawl space.  I pulled out the old liner and any other junk that was in there.  I closed off all the vents and sealed them up.  Then I began putting up a 6mil liner with construction adhesive and super-all-weather gorilla tape.  Why a 6Mil liner vs the 20Mil liner above?  Well...first...a 20mil liner is like a frickin' pool liner.  The stuff is tonka.  Well, 6mil is more than strong enough since I don't store anything in my crawl space so why do I need something super heavy duty?  Anyhow, after putting down the liner I then sealed up the attic door (built a frame and put on weatherstripping). 

Overall,  it turned out great (I'll post some pics later).  The crawl space does not smell moldy/musty anymore.  The dehumidifer did a great job lowering the humidity from 78% to 48%.  I got worried for a while because my power usage shot up (I think the unit uses around 700W? And yesterday I used 44 kWh..yikes!) and stayed up for about 2 days, but its now caught up and turned off with the humidity is holding steady.

Now I have to recovery from my sore back and legs from working down there for so long...