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Heat or AC?
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03-28-2014, 10:00 AM #1
eaadams Concrete Moisture Expert *****
Status: Offline Posts:591 Threads:85 Joined:Jul 2010
Have slab 99%/60F, 5 months old, done right (stego, no sand, drying top only) ambient is 47-63%/~65F during 72hrs, subfloor surface temp is 56F

They are ready to have AC or Heat running.

I know we want to have lower ambient air RH and in this building we have / will have when turned on RH controntrol of the ambient air.

BUT... do we want a high temp (heat - say 90deg) or cool (AC - say 70deg) for optimal drying conditions?

04-02-2014, 08:18 AM #2
CC Solutions Concrete Moisture Evangelist *******
Status: Offline Posts:1,065 Threads:69 Joined:Dec 2009
Evan,
Warmer air will hold much more moisture than cooler air so you would look toward keeping the ambient conditions warm.
A unit of moisture found in a unit of warm air results in a much lower RH than that same amount of moisture in cool air.
You can look at a psychometric chart to see this relationship.
Moisture will always move to balance the relative humidity between the concrete and the surrounding air. So by keeping the air warm you lower its RH, and draw moisture from the slab more quickly than if the air were cool and had a correspondingly higher RH. Wink

JD Grafton
Concrete Answers for Flooring Problems
JGrafton@ccsolves.com

04-02-2014, 08:26 AM #3
eaadams Concrete Moisture Expert *****
Status: Offline Posts:591 Threads:85 Joined:Jul 2010
Jason should do a video on the psychometric chart

04-07-2014, 11:22 AM #4
eaadams Concrete Moisture Expert *****
Status: Offline Posts:591 Threads:85 Joined:Jul 2010
A good primer on how to read one. I haven't read it (will take some time) but for the forum's benefit: http://www.powerknot.com/how-to-read-and-use-a-psychrometric-chart.html

PDF Imperial (F) - http://www.uigi.com/UIGI_IP.PDF
PDF Metric © - http://www.uigi.com/UIGI_SI.PDF

I've never seen a chart MORE in need of an ipad app.

But I still don't get how to read it for 'units of moisture'

04-15-2014, 03:04 PM #5
Ernesto Concrete Moisture Expert *****
Status: Offline Posts:606 Threads:33 Joined:Sep 2009
(04-02-2014, 08:26 AM)eaadams Wrote:  Jason should do a video on the psychometric chart

Agreed

Stephen Perrera dba
Top Floor Installation Co.
http://www.tucsonazflooring.com
http://www.floorsavior.com

08-11-2014, 02:38 PM #6
eaadams Concrete Moisture Expert *****
Status: Offline Posts:591 Threads:85 Joined:Jul 2010
Jason should do a video on the psychometric chart

08-11-2014, 04:04 PM #7
eaadams Concrete Moisture Expert *****
Status: Offline Posts:591 Threads:85 Joined:Jul 2010
So.....

Slab became cooler & RH went up.

So ... what do I say? The slab cooled so the RH in the slab went up. It isn't a sign that there is moisture in the slab, it is just the nature of RH vs Temp?


7/25/2014 7/29/2014 8/1/2014 8/8/2014

Ambient Air RH 31 31 40 43
Ambient Air Temp 85 85 82 74

Probe 1 91 91 91 92
Probe 1 Temp 74 75 77 73

Probe 2 85 82 82 83
Probe 2 Temp 74 77 77 73

Probe 3 90 85 86 89
Probe 3 Temp 74 79 79 74

Probe4 89 90 90 92
Probe 4 Temp 77 80 81 77

Probe 5 95 92 93 94
Probe 5 Temp 74 79 78 73

Probe 6 93 91 92 92
Probe 6 Temp 73 79 77 73

Probe 7 93 93 92 92
Probe 7 Temp 76 80 80 75

Probe 8 93 92 91 92
Probe 8 Temp 73 78 78 74








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