24x12 shed.. need cooling advice.

[toddwallac]

I built a 24x12 shed/workshop for my leather working.. shed uses smart siding.. insulation between studs and sheetrock interior. roof is pretty much flat with that roll on asphalt roofing and ICE and Water barrier under it. the decking is the solar barrier (silver backing).. I have the roof insulated as well and a wood tongue and grove on the ceiling.

I have been using a Black and decker 14,000 BTU portable AC and its just not keeping up.. I then added to 10" attic fans at each end of the shed.. ceiling fan to move the air around. sealed doors and all around the room line..

The shed runs a few degrees cooler than outside temp but we are now in the 90's in texas.. I was thinking about running some more electrical out to the shed and add a split AC unit but really didn't want to doll out more cash if I don't need to.. I thought the 14,000 portable AC should be able to keep up but its really not.. Shed takes direct heat.. outside temp is now in the 90's.. When I hit the walls with a laser temp, they show around 90.. inside the shed is like 88..

Any thoughts before I spend the money on the split unit AC?

 

[Firebrick43]

First you say the walls and ceiling are insulated but neglect to say with what kind and how thick

All portable ac are inefficient but single hose ones which I think yours is are doubly so.

They not only have the heat producing motors and such inside but try to expel it out side but pull air that’s somewhat cooled and expels it outside as well which de pressurizes the building and makes up that air by drawing hot air in with leakage.

A twin hose unit at least doesn’t do that but still leaks some heat inside from the pump/compressor.

Get a split unit and it will work better, much better and will repay you in saved electricity.

 

[toddwallac]

First you say the walls and ceiling are insulated but neglect to say with what kind and how thick

All portable ac are inefficient but single hose ones which I think yours is are doubly so.

They not only have the heat producing motors and such inside but try to expel it out side but pull air that’s somewhat cooled and expels it outside as well which de pressurizes the building and makes up that air by drawing hot air in with leakage.

A twin hose unit at least doesn’t do that but still leaks some heat inside from the pump/compressor.

Get a split unit and it will work better, much better and will repay you in saved electricity.

I used that between studs fiberglass r-13 with the paper side.. put it betwen the studs and stapled it in..

the black and decker portable ac is single hose which is vented outside.. I insulated the exhaust hose as well.. it was producting a lot heat. I have seen some hack videos converting this unit to a dual hose. I can definitely feel the cold air coming out of it and can stand in the middle of the room and feel it hitting me.. with that said, it just can't keep up.. I have been close to pulling the trigger on a split unit.. I am worried about hotter weather as I am in Texas and it will get real hot in July and august.

 

[Firebrick43]

I used that between studs fiberglass r-13 with the paper side.. put it betwen the studs and stapled it in..

the black and decker portable ac is single hose which is vented outside.. I insulated the exhaust hose as well.. it was producting a lot heat. I have seen some hack videos converting this unit to a dual hose. I can definitely feel the cold air coming out of it and can stand in the middle of the room and feel it hitting me.. with that said, it just can't keep up.. I have been close to pulling the trigger on a split unit.. I am worried about hotter weather as I am in Texas and it will get real hot in July and august.

So R 13 is all that is in the ceiling?

 

[toddwallac]

So R 13 is all that is in the ceiling?

yes.. I stapled up the long strips of that fiberglass insulation between the rafters.. the decking on the roof is that solar barrier with the silver backing.. its 2x6's for the roof.. for the actual ceiling is that wood tongue and grove..

this stuff:

https://www.lowes.com/pd/Johns-Manville-R-13-Fiberglass-Batt-Insulation-with-Sound-Barrier-23-in-W-x-93-in-L/3006486

 

[toddwallac]

This AC: https://www.amazon.com/BLACK-DECKER-Portable-Conditioner-Display/dp/B01DLPUWJ4?tag=atomicindus08-20

this fan at each end of the shed:

https://www.amazon.com/dp/B07T75SS7V?tag=atomicindus08-20

 

[mike93lx]

So you are blowing hot air through the building with attic fans?

 

[toddwallac]

So you are blowing hot air through the building with attic fans?

well.. they blow outward so was hopeful it was sucking hot air from the inside and blowing it out side..

 

[mike93lx]

well.. they blow outward so was hopeful it was sucking hot air from the inside and blowing it out side..

Where is the replacement air coming from?

Outside

 

[toddwallac]

So R 13 is all that is in the ceiling?

I actually forget if it was R19 or R13 but take from your post, it should be more.. would have to pull down the tongue and grove which is not a Huge deal but if that would help. Would it be worth it to tear down the ceiling and put r38 there or just do the split unit?

 

[mike93lx]

I actually forget if it was R19 or R13 but take from your post, it should be more.. would have to pull down the tongue and grove which is not a Huge deal but if that would help. Would it be worth it to tear down the ceiling and put r38 there or just do the split unit?

The reflective coating on the sheathing needs an air gap to be of any use.

Don't jamb insulation in... It needs to be uncompressed. If you can modify the ceiling to accept something like r30, it would certainly help.

I'd start with a better a/c. Even a window/through wall would be better than a portable. Minisplit would be best

 

[toddwallac]

Where is the replacement air coming from?

Outside

good point.. the portable AC is running during the hotter parts of the day and the fans kick on at higher temps... right or wrong, I thought the fans up along the roof would **** out how aire and draw the cooler air from down low where the portable AC is..

 

[mike93lx]

good point.. the portable AC is running during the hotter parts of the day and the fans kick on at higher temps... right or wrong, I thought the fans up along the roof would **** out how aire and draw the cooler air from down low where the portable AC is..

Sure, but new air needs to replace what you are blowing out. So you are really just sucking out conditioned air and pulling in unconditioned.

 

[toddwallac]

Sure, but new air needs to replace what you are blowing out. So you are really just sucking out conditioned air and pulling in unconditioned.

I turn the fans up to a much higher temp to kick on to see what the AC is able to do

 

[mike93lx]

I turn the fans up to a much higher temp to kick on to see what the AC is able to do

Its not helping. It's getting hot in there because your a/c can't keep up then you are pulling in even more unconditioned air.

 

[Firebrick43]

I actually forget if it was R19 or R13 but take from your post, it should be more.. would have to pull down the tongue and grove which is not a Huge deal but if that would help. Would it be worth it to tear down the ceiling and put r38 there or just do the split unit?

R38 is minimum fore good reason.

Also I imagine its unvented rafter bays and insulation is touching the roof deck? Look up “cathedral ceiling damage” in google and see what an invented bay will do

Foam, either spray or cps/eps installed tight and foam gun sealed around the perimeter can be used to make a hot deck and then fiberglass under. Or you need to vent and leave air gaps.

To give more depth you can make false rafters by nailing on some 4”x 12” x3/8 ply on both sides of the rafters, probably in three places for each rafter and a 2x4 on the end of the ply.

 

[Copymutt]

Just a thought. Sounds like its a solar collector, being flat black roof. 70% Shade cloth spanning the structure would cure the radiant gain. Not overly expensive. Then the AC would have a chance.

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[toddwallac]

The reflective coating on the sheathing needs an air gap to be of any use.

Don't jamb insulation in... It needs to be uncompressed. If you can modify the ceiling to accept something like r30, it would certainly help.

I'd start with a better a/c. Even a window/through wall would be better than a portable. Minisplit would be best

the roof rafters are 2x6's with the existing insulation and its not compressed down. so.. top to bottom is..
1) roll on roof
2) Water & ICE barrier
3)Solar Board Decking
4) 2x6
5) paper faced insulation between 2x6's
6) tongue and grove ceiling

When measuring the ceiling with a laser temp, it was around 87 degrees.. but where the celling and walls meet seemed to be the hottest at 91 degrees.. walls seem to be around 87 also.. there is a 8' fence around the shed blocking some sun but the roof and top of the shed are direct sun.

 

[toddwallac]

Just a thought. Sounds like its a solar collector, being flat black roof. 70% Shade cloth spanning the structure would cure the radiant gain. Not overly expensive. Then the AC would have a chance.

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How would you put that on? just drape over the roof resting on the existing roof or build a frame for it? since the roof doesn't have a lot of pitch would worry about water pooling on it and weighting it down. I could pull it tight and staple it to the sides along the drip rail unless it needs to be raised off the roof.

 

[mike93lx]

How would you put that on? just drape over the roof resting on the existing roof or build a frame for it? since the roof doesn't have a lot of pitch would worry about water pooling on it and weighting it down. I could pull it tight and staple it to the sides along the drip rail unless it needs to be raised off the roof.

It would have to be raised so air can flow underneath.

Think of it like an umbrella casting a shadow

 

[toddwallac]

This is basically my shed that I turned into my leather working shop.. the modifications are the door is a single medal door and is not centered.. its at the end and I made the shed longer than pictured.. there is a car port area for my riding lawmower and weedeaters, etc.. It has a sliding barn door.. The real reason for this design was to keep it low and not visibile from the street as the HOA would not approve anything visible from the street.it does have a fence around it.. the roof doesn't have much slope to it which I wish I had done differently as I had to use water barrier and roll on roofing. With that said, it does not leak.. its painted a very lite beige color matching the house.

I do like the idea of a shade cloth blocking the sun but not sure how to put it on without building a structure for it.. I am thinking of just putting the mini-split and over power the hot air..

does anyone have a recomendation on a mini-split that is somewhat a DIY and run on 110? its about 50 feet from where my breaker panel is.. currently I have a 110 circuit to the shed and was going to run another 1 or 2 ciruits from the shed. This has grown from storage to workshop..

 

[mike93lx]

https://www.lowes.com/pd/MRCOOL-DIY-4th-gen-ENERGY-STAR-Single-Zone-12000-BTU-22-SEER-Ductless-Mini-Split-Air-Conditioner-and-Heater/5014450471

 

[Copymutt]

You’ll need to be a little creative & fab up some stand offs from the roof/ wall edges. Typically the shade is attached via bungie or tiewraps through grommets which you can specify location & frequency.
No issues w/ rain as they wont hold water. At 12x24 cross support will mitigate sag. Something like aluminum tube or 3/4 - 1” pvc would be appropriate, no chafing, light weight.
Here at high altitude intense sun the concept works remarkable well & they are UV impervious.

 

[Firebrick43]

The 110v thing had me curious as 12000 btu is about the limit on minisplits. Most 18,000 btu ms units are 220v.

Interestingly B&D 14,000 btu rating is sort of like the 5 hp air compressor ratings, per BS

They use the old ASHRE rating test done at 80 degrees and 51% RH and then in little notation state that the new ratings are 7700 btus.

The MR Cool linked above is using the new testing method at 95 degrees

https://cdn.shopify.com/s/files/1/0...o_12K_BTU_AHRI_Certification.pdf?v=1658943144

Plus it’s not drawing in hot make up air because of the single window duct.

 

[toddwallac]

The 110v thing had me curious as 12000 btu is about the limit on minisplits. Most 18,000 btu ms units are 220v.

Interestingly B&D 14,000 btu rating is sort of like the 5 hp air compressor ratings, per BS

They use the old ASHRE rating test done at 80 degrees and 51% RH and then in little notation state that the new ratings are 7700 btus.

The MR Cool linked above is using the new testing method at 95 degrees

https://cdn.shopify.com/s/files/1/0...o_12K_BTU_AHRI_Certification.pdf?v=1658943144

Plus it’s not drawing in hot make up air because of the single window duct.

getting an electrician to come out to quote running another circuit or two.. looks like the lowes by my house have them in stock.. once I have power, install looks pretty straight forward.. if anyone has installed a mr cool, would love to hear how it went. the lines look to be preloaded and I don't seen anything about needing to vacuum the system..

 

[toddwallac]

You’ll need to be a little creative & fab up some stand offs from the roof/ wall edges. Typically the shade is attached via bungie or tiewraps through grommets which you can specify location & frequency.
No issues w/ rain as they wont hold water. At 12x24 cross support will mitigate sag. Something like aluminum tube or 3/4 - 1” pvc would be appropriate, no chafing, light weight.
Here at high altitude intense sun the concept works remarkable well & they are UV impervious.

well.. I am the king of creative.. I found this one which looks like it would work for me:

Amazon.com

PVC seems easy but don't want to block drainage on the bottom side.. and don't want wind to take it way..

was thinking of using 1" pvc pipes like a post and thread a wire stringer around it attaching the grommits via tie wraps..

 

[BillK]

Is there a window ? Last summer our AC decided it had lived long enough and of course it was 90 degrees every day. While I was replacing the condenser I went to Lowes and bought a cheap 110V window unit. I put it in our master bedroom window and darn if it didnt almost cool the whole 2200 sq ft house to a comfortable level. I am sure it would be more than enough to do the job in your workshop.

 

[Firebrick43]

getting an electrician to come out to quote running another circuit or two.. looks like the lowes by my house have them in stock.. once I have power, install looks pretty straight forward.. if anyone has installed a mr cool, would love to hear how it went. the lines look to be preloaded and I don't seen anything about needing to vacuum the system..

I prefer Mitsubishi as you can trim the lines and they are better but before one of the other guys realized I had a vacuum pump the bought a Mr cool for a 28x24 addition (24000 btus and it’s pretty good other than the wad of extra line set.

 

[toddwallac]

Is there a window ? Last summer our AC decided it had lived long enough and of course it was 90 degrees every day. While I was replacing the condenser I went to Lowes and bought a cheap 110V window unit. I put it in our master bedroom window and darn if it didnt almost cool the whole 2200 sq ft house to a comfortable level. I am sure it would be more than enough to do the job in your workshop.

I don't have any windows in it...

 

[mike93lx]

I don't have any windows in it...

A window and a 12k will be a lot cheaper and easier than a mini split.

A midea u shaped 12k is about $450 and a cheap double hung is $200-300

Midea 12,000 BTU 115-Volt U-Shaped Smart Inverter Window Air Conditioner Wi-Fi, for up to 550 sq. ft. MAW12U1QWT - The Home Depot

Window AC Reinvented - meet the Midea U! Introducing the first ever U-shaped Inverter 8,000 BTU window air conditioner that allows you to open or close your window while the unit is installed. The innovative

www.homedepot.com

 

[WildBill]

Cheapest would be cut a hole for a normal window AC, it will work a million times better than that portable one with a hose. Those are a joke. Second would be cut a hole for an inverter window AC, even better and more efficient. Third would be a minisplit, be much nicer but will cost you at least 3X as much as a window inverter unit by the time you add all the little bits. I put a 24k Mr.Cool in my shop a couple years ago, it works great and was pretty easy to install. Make sure and add a surge protector at the outside disconnect as the control boards are really sensitive in minisplits. And use Nylog on the fittings, as well as the proper torque settings.

 

[Copymutt]

Did this 2 yrs ago. No more blistering sun on the bedroom exterior walls. No need for AC & looks nice. Less than $400.00

 

[toddwallac]

ok.. electrician was out and running a proper power to the shed. He said he could have his AC guy put in a 12,000 split unit for $1K installed.. the unit has wifi, heat, etc.. are these all created equal or is the mr. cool unit better.. he said he would have his guy call me.. $1,000 installed sounds better than $1,700 and I have to install.. I think my fans were as waste of money but I can vent humidity for fumes out if I need to..

 

[mike93lx]

ok.. electrician was out and running a proper power to the shed. He said he could have his AC guy put in a 12,000 split unit for $1K installed.. the unit has wifi, heat, etc.. are these all created equal or is the mr. cool unit better.. he said he would have his guy call me.. $1,000 installed sounds better than $1,700 and I have to install.. I think my fans were as waste of money but I can vent humidity for fumes out if I need to..

1k installed is too good to be true. He must be wrong or it's absolutely garbage equipment

 

[toddwallac]

turns out it is.. getting quotes at $1,400 - $1800 installed but can't get the brand they are using understood

 

[mike93lx]

turns out it is.. getting quotes at $1,400 - $1800 installed but can't get the brand they are using understood

I wouldn't trust the equipment or installer at that price

The cheapest 12k minisplit on SupplyHouse is $870 excluding a lineset

Lineset, markup, equipment time, warranty electrical all for well under a grand?

https://www.supplyhouse.com/Bluefin-BFMS1221BA-01-Bluefin-Basic-Single-Zone-12000-BTU-SEER2-21-4-Ductless-Mini-Split-Air-Conditioner-and-Heat-Pump-w-WIFI-Package

 

[toddwallac]

brand is that confortotal with the red, blue and yellow triangles... 12,000 btu with wifi... just got pictures of the unit..

 

[mike93lx]

No idea. Maybe it's a diamond in the rough

A window unit will be alot easier to swap out when it fails

 

[toddwallac]

so.. its mr. cool for $1,700 and I install or Confortotal installed for $1400.. This is Texas so it gets hot and cold.. both units are 12,000 btu's.. googling Confortotal the only negative was a complaint it could not keep up with really cold.. below 32 which it does get to here from time to tome but I am not living in the shed.. just need it comfortable when I am working there..

 

[toddwallac]

how good are these heat inverters? This is the unit I found that looks like the unit:

Mini Split Confort Total heat pump inverter wifi - CONFORTOTAL

12,000 BTU Ductless Inverter Air Conditioner, Heat Pump 110v 1 ton With/Kit. Mini Split Confort Total heat pump inverter wifi.

www.airesconfort.com

it looks like its $500 for the unit.. The Mr. Cool is $1,700.. what would a $1,200 difference be?

looks like the Mr. Cool is a 22 SER and the Confortotal is 18 SER