Friedrich Window Thru-Wall

[Steve DeMars]

I am in the process of building a woodworking shop.

Location - Baton Rouge, LA - high humidity area

Two small 3' wide X 2' high insulated windows facing south very near the top of the walls.

Size will be 20' X 22' (440 sq. ft.) with 10' ceilings.

Walls will be 4" - drywall / R-13 batt / 3/4" fiber type blackboard / Hardie Plank.

Ceiling will be - drywall / R-49 batt / to open attic.

Attic will be well ventilated with (2) 14" turbines.

Roof will be shingled with Solar Board for roof decking.

Looking at 12,800 / 13,200 BTU cool only unit from Friedrich (only one I could find with a good reputation and USA made) EER 9.5, moisture removal 3.3 pints/hour, 280 CFM, 6.3 AMPS, cooling watts

1389.

Is this size unit going to be enough. I want cool, don't want short cycles & no humidity removal . . .

Any suggestions appreciated . . . . . Steve

[ATP*]

Are you venting anything outside? That will significantly impact the cooling load. Motors can add considerable cooling load as well. Grainger's has some sizing suggestions in their catalog, or local sources should be able to advise you. You may have to compromise on cooling in the hottest weather if you want to avoid short cycling in the shoulder months.

[Jim Stuyck]

In suburban Dallas/Fort Worth -- my location -- I have a similarly sized workshop/garage with an 8'-4" ceiling. My unit is 10,000BTU. It works pretty good in the summer IF I turn it on "early," before it gets hot. Frankly, I'm pleased with my setup. I can work at 76F, it's not on "all the time," and it pumps out the water. Mine is a "Hampton Bay" that I got at Home Depot just over three years ago.

But with your 10' ceiling, and higher humidity, I'd be thinking more capacity than what you have described.

Jim Stuyck

[Upscale]

Isn't the real problem humidity, not so much the heat? What about a dedicated stand-alone dehumidifier and if necessary, a lesser btu airconditioner? I know air conditioners can accomplish both, but as I understand it, not as well as a dedicated dehumidifier.

[Charlie Self]

As someone who runs both, I suggest that you strongly not consider running a dehumidifier alone if you want to stay comfortable. We add an extra to the basement, but the heat it turns out is comparable to the heat you'll find coming out of an AC. Not as strong, sure, but it will heat up a small room in a rush. We've got central air, but the basement tends to dampness, which is a nuisance, and we run the dehumidifier as a supplementary water removal source. As a comfort device alone, it doesn't seem to me it would be worth much...actually, if it were my decision alone, I'd toss the thing in the trash, but someone once sold my wife on the efficacy of this appliance, so...for ten bucks a month in electricity, life is quieter.

[Upscale]

I wasn't thinking of the running of a dehumidifier alone, but in conjunction with a lower BTU airconditioner. (for those that aren't on central air). I was thinking of lower electricity costs overall. Of course, my last experience owning an air conditioner was a good twenty years ago. It's likely that the technology of air conditioners has improved from what I knew. For the past several years, it's only the cold that bothers me. Even in the latest Toronto high humidity climate which is equivalent to 40+°C (102°F), I'm fine with a fan and nothing else.

My plan for when I win the lotto is to move down to some part of the USA that is warmer and flatter. Don't know what I'm doing up here for five months of the year in this damned Canadian winter.

[Mark & Juanita]

Steve,

Try the following link: Using their computations and allowing using the room including a kitchen to estimate various shop loads as well as loading with 4 persons, they indicate 15,500 BTU. 10,000 BTU is the low end of their estimates for the size room you are projecting.

Another rule of thumb is 6 BTU per cubic foot, since you are going to have about 4400 cubic feet, that translates into about 26,000 BTU, a little over a 2 ton unit. The one you are considering might be a bit small.

+--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+

[Mark & Juanita]

... snip

^^^^^

Got something else on your mind there ATP? ;-)

+--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+

[Edwin Pawlowski]

That would sound about right.

Overkill. You can do a small house with that unit.

[O D]

If you want cool you must remove humidity. You will not cool till you lower the dew point of the air. And the longer you run the unit the more moisture you will remove. The window shaker is just like a dehumidifier except that the condenser ( HOT ) side is outside, On a dehumidifier the condenser and evaporator (COLD ) side are both inside, So you can see where you are heating the room up with just a dehumidifier as the compressor is adding heat and all that heat stays in the room. With the window shaker the condenser rejeects the heat outside. If you want a ball park size then we use to use 6 btu per c/f. But I will tell your right now you will not be happy with this figure as the unit will be overside and the unit will cycle on and off. And when it is off not moisture removal. Kind of loke a cold beer on a hot day . With the bottle full. you cet condensation on the outside of the bottle. Two inutes later bottle empty no more condensation . Translation ...... Ya need more beer. momma bring me another cold one will ya, there is just too much humidity in here. Also if you deside to dehumidify the room this way, please don't use any machinery cuz it is gonna take me a long long time to do this.

[Mark & Juanita]

Yeah, that seemed really large when I applied the 6 BTU / ft^3, even with

8 foot ceilings, that comes to 21,120 BTU. When looking back at my notes, I can't find a source for that "rule of thumb".

+--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough

+--------------------------------------------------------------------------------+

[Robert Bonomi]

You've got three sources of 'thermal load' in that shop: 1) heat that comes in from outside world. thermal conductivity of walls, etc. 2) people in the shop 3) equipment, et al.

1 amp of continuous electrical use, at 120V, equates to roughly 410 BTU/hr. (alternately, 1 kilowatt-hour equates to 3414 BTUs

One person, doing light work, generates about 650 BTU/hr. Doing sustained

*very* heavy work, around 2400 BTU/hr. Guesstimate, for typical wood-shop work, in the 1000-1200 range.

I get around 5,000 BTUs for thermal conductivity, assuming a 15 degree F temperature differential, and *no* direct sunlight on the structure anywhere.

Add another 3400 BTUs for each wall that is exposed to direct sunlight. Add roughly 1000 BTUs if the roof is in direct sunlight.

This is what it takes to -maintain- the temperature difference. You need more than that to get things down to the desired temperature in the first place.

Making some "WAG" assumptions about sunlight/shade, it looks like the unit you're looking at is 'barely adequate' at best -- it looks like it will max out with 1 person in the shop, and _no_ lights/tools/etc other than the A/C running. Guessing you probably want about 15,000 BTUs. maybe as high as 18,000.

Sanity check: the house I grew up in, had an upper room that was exposed to outside on 4-1/2 sides (3 walls, roof, and 1/2 of fourth wall), about

360 sq. ft. we had a _supplemental_ 12,000 BTU unit in that room, over and above the household central A/C. And the locale was considerably farther north (latitude 42N, almost exactly).

[Charlie Self]

Robert Bonomi wrote: .

Right now, I'm under air conditioned, as today proved. Hit about 95 outside, shop rose to about 82. My two tiny window units will not pull the place down. I have to either leave them on all night, or start them when I first get up (about 4:30 most mornings). Even then, it creeps upwards. But I'm cooling a 25x48 building, 9' ceiling, almost no ceiling insulation yet (and tin roof). For an 8000 Btu unit and a 6000 Btu clunker, it could be a lot worse. I'm a bit bugged at a couple outfits that owe me money, as the local WalMart had 10,000 Btu ACs on sale last week, for $194 each. There were six. I had planned to grab two to replace my underpowered units. They're gone now, and the damned checks still haven't come.

I guess buy a new lens now, and grab the last of the season next month when they go on sale. I think probably two 11,500 units will work better anyway, and they will use 220, instead of 110, which will make me happier.

[Larry Jaques]

So buy a case of construction adhesive and some sheets of 2" rigid foam insulation to toss on the inside of that shop roof, Charlie. Get that place -insulated- before you spend any more money on new a/c units, eh? With proper insultion, you may not need new units. Older boxes are less efficient, so it may be that you need to replace them anyway, running-cost-wise.

That said, I should drill and foam the shop wall on the west side of the house some day soon. It runs 5 to 8° hotter in the summer and colder in the winter than the rest of the house. (Remember? I bought a

2-car shop with attached house.)

A/C lens?!?

[Robert Bonomi]

You're *definitely* under-provisioned. I get 9,000+ BTUs through the walls (Assuming R-13 insulation) alone at a 15 deg F differential w/o any direct sunlight. Plus about 150 BTUs per linear foot of wall exposed to direct sun.

With good (R-30+) insulation for the ceiling/roof, another 2500 BTUs or so through the roof. 4,000 BTUs more, if the roof is fully exposed to direct sunlight. With just a corrugated tin/steel roof, scale those numbers up by a factor of _at_least_ FIFTEEN.

I see around 11,500 BTU/hr conduction through good insulation, if fully shaded. _Another_ 11,500 or so, if it is 'mostly' exposed to the sun.

Before considering the 'people load', or the electrical consumption.

Guesstimating you'll need a pair of 13,500 units -- at least. I'd be looking at a pair of 15,000s -- to get 'reasonable' cool-down from the 'unconditioned' state.

*AFTER* doing something to insulate the roof, that is. Going from 'no' (for all practical purposes) insulation to 'decent' insulation, pays for itself *extremely* quickly. Just a suspended ceiling grid, with the 2" blue board insulation on it -- with some decent air circulation *above* -- can make an incredible difference.

[Charlie Self]

It's partially insulated now, with a few gaps. I plan to blow in insulation this winter, probably 8-10" which will cover the joists. Right now, only someone a lot younger than I am would attempt working under that tin roof. It's only 86 out right now, but...

Actually, a friend and I just finished unloading three jointers, with two in the normal two package configuration, and one packed as an assembled unit--at about 750 pounds. That one was enough for us to use a come along and an eyebolt I had installed in the wall years and years ago and never used before. I don't know how the HELL I'll get it repacked and loaded for shipment. I may have to take it apart and make two crates. A fun morning.

[ATP*]

Fenestration