Southwest Florida heat & humidity, help!

[tjstrain]

My garage is a 45 by 55 steel building with 1” of foam board insulation and finish, EFIS. Also batt insul. on the inside, all walls and roof, not sure what the thickness is, but it scales out to about 4" on the drawings. Inland Buildings is the manufacturer of the structure. So, it’s about 2475 sq. ft. and 42,075 cubic feet. Being in southwest florida it gets hot and humid as hell in there. I’m in need of ventilation for the whole thing and A/C for the proposed enclosed area to be built. Right now I just open the doors and windows whenever I’m there but that is not everyday. I’m afraid that my items stored there will begin to rust over time. The other factor that I’m concerned about is the occasional break-in. Since my garage is in a residential neighborhood which is on a main road that has lots of exposure. There are quite a few “low rent” houses around and my place and it gets everyone gawking at it as they drive by. I do have an ADT alarm system in place so there’s slight peace of mind.
What I’m thinking of is using a window ac unit, which will be in the new enclosed area. But, I’m gonna have to build a secure cage around it deter any intruders from finding an easy way in. With the way the economy is here you never know. Now thinking about it maybe I’ll leave the hurricane panels on the window and put the window unit thru the wall instead, just higher up, but still with a cage around it. I’ve got to many dollars invested in tools and toys there to take a chance. Maybe I’m paranoid but I’d rather be safe than sorry.
Is there some kind of big unit I could use for the whole building or should I just concentrate on the proposed enclosed area?????
Did I mention that it’s gotta be HURRICANE proof and not compromise the pressure factor inside the building when a CAT 4 hurricane blows through. I really don’t want to AC the whole building 24/7 due to cost.
What’s a guy to do when it comes to his toys?

Hurricane panels installed on all windows for privacy/security.

This side is where I am going to put a second floor for storage. Left side of the door the ceiling height will be 8', office and bathroom. The right side will be 9'4" ( so we can roll in a lifted vehicle or trailer) enclosed work area proposed for the right side with the window.

looking at the inside of the front wall.

 

[tjstrain]

Painted a new color outside.

It's getting to small already!

It gets quite steamy in there during the day.

 

[redsky49]

You are conveniently located in one of the hotter spots in Florida. You will have to decide on two issues prior to offering any suggestions:

1. What interior temperatures do you expect to maintain? What operations will be performed in this space?

2. How much are you willing to spend?

Your space is bordering on a commercial, rather than a residential application. A proper HVAC system will not be cheap.

 

[tjstrain]

1. What interior temperatures do you expect to maintain? What operations will be performed in this space?

Looking to prevent corrosion basically when I'm not there in all of the space.( Ventilation) When i'm there like it be be comfy enough to work on restorations or maintenance without getting dripping wet. (Air conditioning)

2. How much are you willing to spend? I'm open to suggestions. What's the best bang for my buck? Without airflow in the building, during our rainy season which is now, vehicles will prolly start to corrode faster inside than out.

Your space is bordering on a commercial, rather than a residential application. A proper HVAC system will not be cheap. yes I agree on the commercial application.
With all of the foreclosures here and it seems that all of those loosing their homes are also selling everything connected to those homes, including their AC units. maybe I can pick one up fairly cheap.????

 

[Falcon67]

Maybe consider two systems - IIRC, 2400 sq/ft in a house is right on the dual system border. You could use a big system - 4-5 ton? not an AC guy- for the main area as it will not be run as much and a smaller "split" system ( like this: http://www.minisplitsystems.com/ ) for the enclosed work area.

I would not consider any window unit - 1) not any big enough 2) big ones not nearly as energy efficient as house/commercial systems 3) a good sized hole in the wall gives a place for vandals to enter the building.

 

[tjstrain]

thanks for the info so far, keep it coming......tj

 

[redsky49]

Okay, first let's throw out some ground rules.

Opinions offered here are for discussion purposes only. All final design decisions are the responsibility of the original poster, which should be made in consultation with a qualified local expert.

No dangerous or hazardous operations will be performed within the structure, nor will toxic or flammable materials be stored other than in small (safe) quantities.

By code, all occupied spaces must be ventilated. That means that outside air has to be introduced into the space. Ventilation is either by natural means (windows and doors) or is done mechanically by fans and/or operable dampers. Natural ventilation requirements are satisfied if the operable opening is at least 4% or more of the area being ventilated. You will need to ensure that both areas of the garage satisfy this requirement. Bear in mind that the Codes view parking/storage garages differently than repair garages. You are responsible for ensuring code compliance per local requirements. In addition, I would recommend that you use at least some full-time mechanical ventilation for the reasons you stated.

All work shall be in compliance with local codes and regulations, including applicable hurricane requirements (I also live in a hurricane zone but am not familiar with the requirements of every jurisdiction).

That being said, I have a few ideas.

I am assuming that the office/toilet area will be in the neighborhood of 400 sq. ft. plus or minus, leaving roughly 2100 sq. ft.for garage/storage. Unless I am wildly off, actual dimensions are not especially critical for this discussion.

The first thought I had was to put a packaged rooftop unit (RTU), 6 to 7-1/2 tons depending on the load, on top of the building, but the roof structure would have to be modified (preferably by the original manufacturer) to accept the new roof curb and the weight of the unit. Looking at the span of the roof members this might be expensive (but not impossible), so off to plan B.

For the office/toilet area I would recommend one of the small split systems that have been discussed at length on this forum. These have several benefits over a thru-wall unit. First, they do not allow an opening large enough for unauthorized entry. Second, the allow some flexibility for placement of the outdoor unit, generally from 50 ft. to as much as 100 ft. from the indoor unit. Third, they would be the least susceptible to wind and rain egress/damage during inclement weather. And finally, the better units have provision for introducing outside air into the space, ensuring proper ventilation. A load calculation should be performed to determine actual unit size (probably one ton or thereabouts).

For the general garage area you said you wished to ventilate - let's look first at ventilation. In hot climates, air velocities that would ensure some measure of comfort would typically be excessive. In other words, trying to cool you by blowing humid 90 degree air at you will have limited effect. The evaporative cooling from the moisture (sweat) on your skin simply will not occur (move to Arizona for this). When the weather is cooperative, you have the doors for comfort. When the conditions are demanding, other steps need be taken.

A device that I have used successfully in the past for small warehouses and manufacturing facilities is known as a VPAC. These are vertical packaged AC units, and are available in air-cooled versions. Picture a box 3 ft. wide, 6 ft. high and 18 in. deep. This would be placed next to an exterior wall, preferably in the center of the garage. A ducted connection would go from the back of the unit to a large exterior louver (which in your case would be protected by manbars).

From the top of the unit a discharge plenum would distribute chilled air throughout the space and in many cases no supply air ductwork is required. This would have to be determined based on your actual layout.

These devices frequently will be provided with what are called "economisers". This allows the unit to use non-conditioned outside air for cooling whenever conditions permit. They also have a part-load cooling capacity provided by compressor cycling and cylinder unloading.

Such devices are very economical to operate, though they have a higher up front cost. They also allow you to filter all incoming air, reducing dust and pollen build-up. With a ducted application such a unit could serve both the office and the garage, though differing operating hours and usages may indicate otherwise in your case. In addition, they are quite easy to service. The better units produce no more noise than your residential furnaces.

A couple suggestions:

Insulate on the interior side of the windows if they are not planned to be used. A simple 2" styrofoam panel, cut to fit snugly will suffice.

Insulate and gasket all edges and segments of the overhead door. Provide a proper threshold strip. Infiltration is your enemy.

Establish a reasonable temperature setting. Try 78 degrees for example. Make downward adjustments in one degree increments, no more than once weekly.

Provide a protective barrier for your insulation in all areas that it may be damaged.

I would also recommend that you check the storm water runoff for your building. I see the splash blocks at the downspouts, but make sure that water runs away from the building.

Hope this is helpful. Good luck with the project. Build something cool in that garage!

As always, offered only as opinion

 

[tjstrain]

Redsky,you said a mouth full! Lots of great info, thanks. Gotta reread it many times to take it all in. Thanks again,tj

 

[4t64rd]

Dehumidifier...? Our A/C guy suggested one for the house...

 

[tjstrain]

I'm still waiting to line up an electrician to run a separate line from the pole to the garage. Then I gotta get FLP to come in and connect the line to the pole. But first I gotta frame in a small wall to put the new electric panel. All this has to be done with a county inspector and permit. Then I can go ahead with framing the walls and supports for the second floor structure, move the bathroom and workbench, then figure out where the AC/ventilation thing will go.