HELP!!!! Building a walk in cooler

[Downey26]

I'm building a walk in cooler in my garage. I have done a lot of research on the project but the only thing I can not find is the R rating i should use for the temperature my garage can get up to. In the summer my garage can get to 100 degree's. I have found rigid polyurethane insulation with an R rating of 9.6, the highest i have found yet. However, they are $26.00 a sheet. The lower R rating of 3 to 5 are cheaper and more cost efficient. My only question is an R rating of 3 or 5 to low? Will the heat penetrate the cooler causing my unit to work more and cost more money in the long run? I have read plenty of articles on the R ratings however non of them suggest a rating for my temperatures. Any ideas or advice? I know it doesn't hurt to go with the more expensive R-rating but a budget means more money to brew beer.

 

[tnorman93638]

I'm also going to be building a walk in cooler in my shop which I'm turning in to a brew pub/brewery. I have done a lot of reading also and found that you need to insulate the walls 1st with a high R value insulation then you add the ridge foam over it. Are your garage walls insulated? I live in the Central Valley and I know how hot the garage can get. Adding cost now by upping your insulation will save money and beer in the future.

 

[chawn]

I think a 4" panel has an R-value of 26 which is the industry standard. Your unit will probably run quite a bit.

 

[damlamb]

I have some experience designing walking coolers. Here is an example of what i use. Ive also included a chart showing the u-value ( 1÷ R value) of various insulating materials. Its probably a little overkill for what you need. Use the highest expected temperature in your garage for the calculations.

 

[damlamb]

Forgot pictures

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[Downey26]

My garage is insulated but not drywalled. The previous owner put some type of particle board which I pretty sure I saw on the show "The Brady Bunch", old school. Im lucky because I'll be able to use 3 existing walls because my garage has a push out section in the back. However the ceiling is open to the roof and isn't insulated which makes my garage so hot.

@Damlamb: I know in commercial walk in cooler they use think foam styled insulation. The stuff I found with an R Rating of 9.4 is sold at home depot and is 1.5 inches thick. with the standard insulation built into the wall and the right air space, do you think it will be sufficient to keep the thermal heat out and cool air in?

 

[raysmithtx]

The R-value lets you calculate how much heat will move through a certain area and depends on the temperature difference between the indoor and the outdoor air.

For example, if you insulate a wall with R-10 insulation and the wall dimensions are 8 feet high by 10 feet long, or 80 square feet and the inside temp is 45 degrees and the outside temperature is 100 degrees, you are looking at a 55 degree temperature difference.

80 square feet * 55 degree F difference / 10 = 440 BTUs

In other words, you will be losing 440 BTUs through the wall continuously at those temps, so if you had a 440 BTU cooling unit, it would be running continuously just to keep up with the heat load. You can use the same info to figure out all of your losses for each wall and ceiling and floor. That will tell you how large a unit you will need (BTU wise) in order to keep the walk in cooler cool and how much insulation you really need in order to strike a balance between the size of the cooling unit and the insulation in the walk in cooler.

The money you my try to save in insulation cost can easily be offset with the cost of running the AC unit to cool it down. And the cost of the insulation is a one time cost and the cost of electricity goes up every year.

Hope this helps.

 

[Downey26]

Thanks Ray My space will be 14x7x4 with your formula i came up with 607 BTU. My A/C unit is 12,000 BTU's, and I knew it was really big for my space.

Now this is probably really dumb question, but if I use R-9.6 Polyisocyanurate Rigid Foam Insulation Board along with the standard attic insulation rated at R-30 does that give me an R rating of 39.6? Or is the A/C unit big enough and the square feet small enough to get away with installing only the Polyisocyanurate insulation?

 

[Shawn-of-the-Dead]

Commercial walk-in insulation varies. The company I work for uses spray foam closed cell insulation. Other companies use polystyrene. If you can get R-25 or above, that would be very good. More importantly, make sure the walk-in is air tight. Any air leakes will led to condensation and possibly mold.

 

[raysmithtx]

...if I use R-9.6 Polyisocyanurate Rigid Foam Insulation Board along with the standard attic insulation rated at R-30 does that give me an R rating of 39.6?

Yes. Insulation can be added together to get the total amount. So if you use some R9.6 on top of some R30 then your insulation value is 39.6.

Or is the A/C unit big enough and the square feet small enough to get away with installing only the Polyisocyanurate insulation?

I didn't run the numbers but with an AC unit that large I'm guessing it would handle the load. Keep in mind that the numbers are in a perfect world and do not take into account air infiltration, opening and closing the door, etc.

I would put as much insulation as I could afford and make sure every seam is caulked and air tight. A common mistake is not insulating the floor. Concrete is not a good insulator and since it carries such a high density it makes a really good thermal battery. That means that it takes a long time for the concrete to change with the seasons. So in the beginning of Winter the floor will still be fairly warm due to the heat it absorbed during the Summer which increases the overall heat load you will be battling.

Also pay close attention to the door insulation and air gaps there.

The more insulation you have and the 'tighter' you can make the chamber, the better off you are.

 

[Downey26]

Thanks for the help everyone. I think I have got it solved. I will post updates on a new thread showing my progress

 

[mucci2k]

I found read this a while ago but it will apply.

https://www.homebrewtalk.com/wiki/index.php/Walk-in_Cooler

 

[locolo27]

Use NSF listed panels, don't throw away your money using foam not especified for food purpose. There no way to control a 4" foam and the density needed for that application.
With time it's going to be saturated with water and u are going to have problems like moisture and fungus in your walls. Whatever other people said or are doing if you are making it between walls at least your panel needs a distance on 2" to 4" inches of separation between walls so moisture don't transfer to outside wall. That's a reality that the ones that make it throwing foam to the walls don't tell you. This kind of insulation only works for your home purpose not for food storage at the end its going to be your problem not the guys that make it for you. I saw this every day in my work. We work refrigeration for kitchen and restaurants and if is so easy out there aren't going to be companies specialized in WIC and WIF. You can't control foam density and 4" thickness throwing foam to the wall if you are going to make it in a second floor you need to make also insulation to the floor. Don't waste ur money. It's going to be cheaper but at the end it's a headache.