Open Cell Spray Foam Isn't Properly Cooling My Portable Building - Insulation - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree1Likes
  • 1 Post By johnssm
Reply
 
Thread Tools Search this Thread
Display Modes
Old 06-09-2018, 05:34 PM   #1
Newbie
 
Join Date: Jun 2018
Posts: 4
Rewards Points: 8
Angry

Open Cell Spray Foam isn't properly cooling my portable building


I recently had a TuffShed portable building built in my backyard. It is 12' X 24' with 8' walls and the ceiling is not vaulted. The shed is on concrete blocks. I then had electricity installed, cable/satellite installed, then had the building sprayed with open cell foam. The walls have 3.5" off foam and the ceiling has 5.5 " of foam. The walls are approx. R-13 and the ceiling is approx. R-20, per the installer.

So, at this point, I have not put up any interior walls, whether it be plywood, paneling or sheet rock. I put a 14K BTU portable AC unit that I had, to see how the insulation would fare. The following afternoon, in the central Texas heat the best my 14K portable unit could do was hold the room at 83-85 degrees F. I was not expecting this. I expected 76 degrees no problem. so the next day I borrowed a friends 8K BTU portable unit and ran both together. That's 22K of BTU. The next afternoon, both portable ac units working together, could not get the room temperature below 84 degrees F. What is going on?

The building gets approx. 6 hours of direct Texas sun.
It is very adequately insulated.
I considered that it was so well insulated, that it created a negative pressure, making it difficult for the portables to push enough air out of the building. SO I opened a window about 2" and that helped to reduce the afternoon temps to 82-84 degrees F. in the afternoons.
That is where I'm currently at. SHould I go ahead and either paint the ceiling foam with an acrylic paint, to further seal the foam?
Do I go ahead and install plywood, paneling, sheet rock?


Why can't I get my afternoon temps down into the 70's at least. THat much portable unit BTU's should have no problem keeping that building cool.
I even insulated the doors with 1.5 inches of open cell spray foam.
The floor is 3/4" plywood, which is not insulated below it. It does have 2 coats of a good paint.


My certified HVAC man has run the numbers on his 'load calculator' and he is completely baffled as well.

Any ideas would be highly appreciated. And if you'd like further information about this building, please ask.


I don't have much hair left to pull out. So please help.


My only idea left to do, is install interior walls over the foam and/or paint the ceiling with a water based acrylic paint.


johnssm is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 06-09-2018, 06:20 PM   #2
Member
 
Join Date: Oct 2008
Location: Ontario
Posts: 6,284
Rewards Points: 11,482
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Quote:
Originally Posted by johnssm View Post
I considered that it was so well insulated, that it created a negative pressure, making it difficult for the portables to push enough air out of the building.
Why is your AC pushing air into or out of the building ? AC is normally a closed system.


Your insulation may be good, but not great. I have R70 over my head right now. But your HVAC guy should be able to run the numbers of what you need.
SPS-1 is online now   Reply With Quote
The Following User Says Thank You to SPS-1 For This Useful Post:
johnssm (06-10-2018)
Sponsored Links
Advertisement
 
Old 06-09-2018, 06:56 PM   #3
Newbie
 
Join Date: Jun 2018
Posts: 4
Rewards Points: 8
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Hi thanks for replying.



The units are portable and they have an hot air exhaust that vents out a window. They also remove moisture through a hose to outside the building, to reduce humidity inside.



I just don't understand why 2 tons of a/c units can not cool the building. And neither can the a/c man I use. He has 20 plus years in the business and he has never seen this before.



If I can ask, how do you obtain R-70?
johnssm is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 06-10-2018, 06:15 AM   #4
Member
 
Join Date: Oct 2008
Location: Ontario
Posts: 6,284
Rewards Points: 11,482
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


I have never used a portable air conditioner, but they don't sound like a good idea. If it is a single hose type, then for every cubic foot of air that it exhausts, it will suck in a cubic foot of hot outdoor air (that is basic physics, no way around it).


Portables don't seem to be very efficient. That may be part of the problem. http://www.budgetairsupply.com/budge...-conditioners/


Minimum code in my area was R-32 or R-35 when my house was built. I added 11" of rockwool bats (R-44) on top of that.


If none of the forum's HVAC guys chime in, you may want to post your problem in the HVAC area.

Last edited by SPS-1; 06-10-2018 at 06:23 AM.
SPS-1 is online now   Reply With Quote
The Following User Says Thank You to SPS-1 For This Useful Post:
johnssm (06-10-2018)
Old 06-10-2018, 07:46 AM   #5
Member
 
Join Date: Nov 2015
Location: Maine
Posts: 10,711
Rewards Points: 224
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Hi John,
Air sealing and insulation are the two factors affecting heat gain and it sounds like the building is tight, except for having to open a window, so that leaves insulation. From your description it does not sound like you have enough, none in the floor (if that is open to the air below), minimal in walls and ceilings, with nothing to reduce thermal bridging. Example, r-13 cavity fill in those walls yields less than r-10 for performance. Depending upon what software your HVAC guy is using that adjustment may need to be accounted for as the numbers go in. Is he using Wrightsoft?

Those single hose portables are considered spot coolers as they cool one location and sacrifice cooling all others. In a large home the sacrifice is shared all over the place so one feels cool next to the portable and doesn't notice the rest of the house being a bit warmer. In a limited space like you have they are not efficient at all.

Is there any attic ventilation and have you checked the temps up there?
What was the outside temp and RH when these ac units were running?

I would first try a normal ac unit in place of the portable, it will give you a better indication of how the insulation is performing. If still not acceptable then you just need more insulation. Maybe an inch or two of rigid over those studs before the interior finish. Same for the ceiling.

Bud
Bud9051 is online now   Reply With Quote
Old 06-10-2018, 11:33 AM   #6
Newbie
 
Join Date: Jun 2018
Posts: 4
Rewards Points: 8
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Thank you for your suggestions. I think I'll replace the portables with a window unit and see what happens. Sounds like I may put up some rigid foam on the walls, if the wall unit under performs. I had one friend tell me to put in closed cell foam on the walls, but the initial cost was much more. Wish I had done that. I'll update in a few days about the wall unit.
Thank you for all your suggestions.
johnssm is offline   Reply With Quote
Old 06-10-2018, 12:09 PM   #7
Member
 
Join Date: Nov 2015
Location: Maine
Posts: 10,711
Rewards Points: 224
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


On concrete blocks so I'm guessing an air space underneath. When you cool the inside that cool air goes directly to the floor. With no insulation it becomes a significant source of heat. No easy solution but on the list if all else fails.

Bud
Bud9051 is online now   Reply With Quote
The Following User Says Thank You to Bud9051 For This Useful Post:
johnssm (06-10-2018)
Old 08-02-2018, 02:13 PM   #8
Newbie
 
Join Date: Jun 2018
Posts: 4
Rewards Points: 8
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Well its been some time, but I had promised to update my cooling problems with the portable building. As I mentioned before, I took out the portable a/c units, and did replace them with a 15K window unit. In the middle of the afternoon, I could hold the temp to 79-80 degrees inside. Well that further frustrated me as I need this building to be much cooler, because of the future contents (computers, radios, food processing equipment). So I removed the 15K window unit and put in a 28K BTU Frigidaire window unit and I can safely say, I have no problem cooling this building, finally. I'm showing 72 F this afternoon (2 pm central) Yes, it's plain brute force, but it will do for now. I will be installing rigid board on the walls, ceiling and another product on the floor. Also considering putting some blow in insulation between the ceiling open foam and the top of the rigid foam, once that is installed. That , I believe should help things further.



A friend said: 'that hot sun beating down on that black roof, with only 5.5 inches of open cell foam, no wonder you can't cool that building'. That put a visual to the situation and I think the ceiling needs more help. Thanks for the past suggestions.
Cooler in central Texas.
Nealtw likes this.
johnssm is offline   Reply With Quote
Old 08-02-2018, 02:48 PM   #9
Member
 
Join Date: Feb 2016
Posts: 2,525
Rewards Points: 4
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Didnít see this post originally. Thatís the problem with the portable units. They may produce 14,000 BTUs of cooling but half of it is being pumped out the window. They do serve a purpose but only for a temporary situation certainly not yours. I feel itís a little deceptive on the manufactures part.


Sent from my iPhone using Tapatalk
BayouRunner is online now   Reply With Quote
Old 08-02-2018, 03:38 PM   #10
Breakin' Stuff
 
Join Date: Mar 2016
Location: Cleveland, OH
Posts: 690
Rewards Points: 1,374
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Foam is a pretty good insulator. The fact that you had trouble cooling this small room is very surprising. I was going to say it's 1 of 2 things, poorly working AC units or lots of air leakage. Since you've put new AC units it, that points to air leakage. How hot has it been in Texas? Only other thing I can think of is it's just crazy hot outside.
__________________
Renovations to my 1947 home can be followed here: www.schlosserhouse.com
Bret86844 is offline   Reply With Quote
Old 08-04-2018, 09:44 PM   #11
Member
 
Msradell's Avatar
 
Join Date: Sep 2011
Location: Louisville Kentucky
Posts: 2,981
Rewards Points: 1,254
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


What kind of air-conditioning are you planning on installing in the long run? Seems like an ideal application for a mini split.
__________________
Written using Dragon Naturally Speaking
Msradell is offline   Reply With Quote
Old 08-04-2018, 11:43 PM   #12
Member
 
Join Date: May 2008
Posts: 730
Rewards Points: 1,251
Default

Re: Open Cell Spray Foam isn't properly cooling my portable building


Something's not right. I have a house at the beach under 700 square feet in size. Walls are fiberglass R13. Ceiling has some blown in stuff (Not sure what it is). Floor has no insulation and is a crawl space. I have an 18,000 BTU in wall unit in the main area. When I'm not there, I don't run the A/C. I run a dehumidifier only. I monitor the house with Wireless Tags. The Wireless Tags sometimes report over 95F in the house during the middle of the summer. When I get there, I turn on the A/C and within 1 hour, the house is down to 72F. If I turn the A/C down as low as it can go, I can get it down to 60F in the middle of the afternoon when it's 95F outside. It gets so cold inside that condensation forms on the exterior of the windows and exterior walls.

I also have open spray foam on the entire envelope of my primary house. In the attic where there are no a/c vents, It doesn't get more than 80F during the middle of a 98F summer day.

I'd have gone with closed cell foam since you only did 3.5" of open cell. Closed cell gets better r value per inch than open cell (almost double).
KHouse75 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Insulate Rim Joists with Canned Spray Foam and Roxul sonnaps Insulation 17 09-06-2015 09:30 PM
Fiberglass vs open cell foam in attic under roof Nhfixit Insulation 6 05-21-2013 10:11 AM
question about spray foam Tonglebeak Green Home Improvement 11 02-04-2010 05:38 PM
closed cell vs open cell foam insulation amonalisa Building & Construction 1 11-06-2008 09:39 PM




Top of Page | View New Posts