Hi, We are getting ready to start building my house in So Fla and I have a couple of questions.

1.  How would you finish the inside of the garage walls?  I want to be able to hang tools, shelves, run air lines, etc.

Is the better way to cover them with plywood so I have a secure attachment for the accessories or ???

2.  What about humidity control in super humid So Fla (for the house and the garages)?

MANY THANKS for your input.

plywood on walls will work


I also live in a super tight home in Florida ................ a properly sized HVAC system will dehumidify the inside

Sheet metal works well in garages, the air lines could be run in the wall like electrical and attachments to the ties.

Thanks much.

On the garage my main concern is being able to add shelves and other things that will attach to the walls which need to be securely mounted and which will evolve. If I knew exactly where things will go, I would mount 2 x 6's on expected attachment points as I gather will be done in the kitchen (for example).

I'll run air lines as suggested!

Fire code requires drywall on common wall with house and ceiling. I would use plywood 1/2 over drywall and 3/4 on remainder and use clear poly to seal. A small window ac mounted in wall sleeve would help keep it dry and much more comfortable. or use a minisplit from mitsubishi or sanyo...9000 to 12000 btu would dry out a well insulated garage/ shop..remember no pvc or cpvc for air lines..Eric

Fire codes require a 1-hour fire rating for common walls between garage & living space, but don't necessarily specify how that rating is achieved. Gypsum board is but one (relatively inexpensive) way to achieve it, and the IRC does spell out minimum thicknesses for achieving that rating with walboard. Half-inch would be the minimum for an empty-cavity wall, but if the wall is insulated that has to be bumped up to 5/8" to meet spec with wood studs. (The insulation causes the fire-side wallboard to fail earlier, since it runs hotter.) If there's a "bonus room" above the garage 5/8" would be required. Some local codes call for 5/8" min even in uninsulated walls, whether or not there is living space above the garage.

If the exterior walls of the garage & doors are reasonably tight a room dehumidifier would be enough to keep up. Setting it to 65% relative humidity would be low enough to keep mold from growing on stuff. If the exterior walls are bare studwalls and you hope to keep it reasonably cool in there in summer it'll have to be insulated & air conditioned. If/how/where to apply vapor control layers depends on the sheathing & siding construction as well as insulation type.

I would have a preference for something waterproof, rot proof and termite proof. Say Hardibacker or fiberglass reinforced plastic panels. Metal peg board in some areas.

Posted By ErVikingo on 10 Aug 2010 09:14 AM
Thanks much.

On the garage my main concern is being able to add shelves and other things that will attach to the walls which need to be securely mounted and which will evolve. If I knew exactly where things will go, I would mount 2 x 6's on expected attachment points as I gather will be done in the kitchen (for example).

I'll run air lines as suggested!

Just cover your ICF wall w/ drywall. Then when you're ready to hang a shelf, or whatever, drill a 1/2" hole through the sheet rock and foam and into the concrete about 2". Drop in a Red Head drop-in anchor using a 1/4" rod & hammer to set the anchor hard, then use a 3/8" bolt of whatever length is needed to fasten the item to the wall. They're inexpensive and you use whatever length of bolt is required for the particular application. They're available at big orange. I used a bunch of them to fasten walls, garage door opener tracks, etc., to the ICF walls.

http://www.homedepot.com/Red-Head/h_d1/N-5yc1vZ1xg6Z19i/R-100154222/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

Thanks, I gather that Hardibacker + drop in anchors sound like the best solution (sturdy moisture resistant base + a mechanichal attachment to the concrete).

A mini split unit will be going in for comfort on the workshop area and I gather for humidity control too.

Thanks again and wish me luck.......

Thanks, I gather that Hardibacker + drop in anchors sound like the best solution (sturdy moisture resistant base + a mechanichal attachment to the concrete).

A mini split unit will be going in for comfort on the workshop area and I gather for humidity control too.

Thanks again and wish me luck.......

most of the name brand mini splits have a humidity control feature...Eric

Posted By ErVikingo on 12 Aug 2010 08:38 AM

A mini split unit will be going in for comfort on the workshop area and I gather for humidity control too.

What mini split system are you planning on using? Will it be for heating primarily, or for cooling, or both? The reason I ask is because my experience turned out not as good as I planned. I have a Daikin 3 ton heat pump with a 36,000 Btuh indoor unit in the house and a 9000 Btuh unit in the garage. In the winter the garage unit would run as I needed. The problem is the garage unit would be the only unit running for much of the time I had it on. Looking at the factory performance charts for the outdoor unit I discovered that with only a 9000 Btuh load on the 3 ton outdoor unit, which it handled quite nicely, the overall efficiency or COP of the system was on the order of 1, the same as straight electric resistance heating. What I should have done was used a 24,000 or 30,000 Btuh unit in the garage then the COP would be closer to 3 or more. But I would have needed to make sure the house unit and garage unit weren't running at the same time because the combined 5 to 5 1/2 ton load on the outdoor unit would have diminished the output of both units significantly.

For heating I solved the problem by installing a pellet stove in the garage. I haven't needed to use the garage unit for cooling very much.

What the mini-split mfrs don't tell you is that the group of connected indoor units needs to be selected and sized so that the all most likely combinations of units running at the same time will load the outdoor unit sufficiently to keep the system at its good to best performance range. This issue caught my HVAC contractor off guard also, and he ain't dumb.

Aren't at least some of the split units inverter driven so that they can vary the compressor output to match the capacity needed?

only an issue with larger multiple indoor unit systems running off a single outdoor unit and there are ways of addressing that issue with relays. newer single indoor systems do not have this issue nor do the inverter driven systems.

Posted By ilgeo on 12 Aug 2010 11:00 AM
newer single indoor systems do not have this issue nor do the inverter driven systems.

You sure? My system is a 2007 built unit with inverter driven compressor, Daikin VRV-S. I can post the performance chart if you'd like to see it.

Here are three graphs of the data I put together from the Daikin manual. Daikin gives the performance numbers only down to 50% connected load so you have to project a best guess when the connected load is only 25%, as it is my case with only the garage unit running. As you can see the performance starts to drop quite a bit when the connected load drops and the outdoor temp drops to the lower end of the design parameters.

Posted By jonr on 12 Aug 2010 10:42 AM
Aren't at least some of the split units inverter driven so that they can vary the compressor output to match the capacity needed?

The capacity is also determined by how much heat the refrigerant can extract from the outdoor air. At the lower end of the design temperature range the compressor has to pump a greater mass of refrigerant to convey the same quantity of heat compared to when the outdoor temp is at the upper end of the design range. The local distributor indicated to me that at the coldest temp a Daikin pumps about 4 times the mass of refrigerant around the loop as does a conventional single speed heat pump. That's why it can extract heat even at 5°F outdoor temp, and colder.

Posted By ilgeo on 12 Aug 2010 11:00 AM
only an issue with larger multiple indoor unit systems running off a single outdoor unit and there are ways of addressing that issue with relays.

True, if the mfr will provide the info needed to tap into the control system. The Daikin is a closed electronic network computer control system where all the units communicate with each other. Not as simple and straight forward as in the good ol' days of simple on-off switching of fans and compressors.

I see nothing that would suggest that COP drops to 1 - or even below 2.

Looks like you may be right. I just did another chart showing COP vs % connected load for 9.5° outdoor, 72° indoor. The low point is at 70% with COP starting to go back up at 40 & 50% load.

Later, when I have more time, I may do another two or three charts at higher outdoor temps just to see how they compare.