HVAC design for a Barn/Shop with an upstairs apartment
My wife and I are in the bid stage for contracting out the building and finishing of a BarnPros barn in the Chattanooga, TN area. The 1st floor will have 648 sf of conditioned space (12×36 shop and a 18×12 tack room) and the 2nd floor apartment will be 1296 sf of conditioned space. As this will be a 2nd home for us, we’re very interested in ensuring we make the right decisions for the HVAC system. There are 10 4’0x4’0 windows in the 36×36 upstairs apartment and 7 3’0x3’6 windows in the shop.
We will also be purchasing a high efficiency woodburning stove (with blower) that will serve as the primary heat source during our stays in the cold winter months. Two of the GCs have indicated that will include a heat pump in their bid, and based on the research I’ve done, this seems like an appropriate choice. But I’m hoping the collective brains here can help me understand the most cost effective route to go to heat/cool the space.
A few questions come to mind …
1) Since I won’t be using the shop all the time, would a split system make economic sense or will the savings simply not be justified by the cost? What other methods/systems could be used to independently control the HVAC for the 1st and 2nd floors? Would a ductless wall unit for the shop makes sense? Anyone had experience with a particular brand that I can investigate?
2) What size system is needed to heat/cool the 1944 sf? Walls will be R-19 and floor / roof of the apartment will be R-30 and the ducts will be run in the insulated space between the floor joists.
3) Are there particular heat pump manufacturers we should steer clear of or run to? One bidder has indicated they will use Carrier.
4) Would blown in cellulose be a better insulation choice over fiberglass batts? One GC indicated we see better performance for very minimal cost, but hasn’t yet elaborated.
Thanks for your recommendations.
Terry
Replies
One possible hang-up: if your jurisdiction requires fire separation between the living space above and the shop space below, it would not allow you to have duct openings into both spaces from one duct system, unless you install fire dampers at points where the ducts pentetrate the fire barrier.
This may not be an issue, but be sure to find out first from the Building Department.
Thanks.
Thanks - someone already reminded me that if i plan to do any finishing work in the shop, the systems would need to be separate or fumes would be pulled into the living space above. That's what prompted me to start looking at two separate systems, just don't know if there are other cheaper or better alternatives.
Terry
Finish work
Also consider ignition sources within the shop area. Both finishing and air born dust can become very dangerous in a shop enviroment.. A dust collection and exhaust system may be needed.
I would also use weather stripping and thresholds at doors between the shop/tack room areas and the living space. It doesn't take much of a pressure differance between the two areas for dust and oders to be drawn from one to the other, as will happen when one system operating and the shop area is not.
Definitly make sure the smoke/CO detectors are woring and tied together. I use dust bonnets to cover my smoke detectors in my shop when I am working there to keep from setting them off with excesssive dust.
I agree that a HP is a good choice for the location, especially since TVA is not an expensive electric supplier.
What kind of shop? If it is a woodworking or an automotive shop, I would suggest separate heating and cooling means. Given the size of the shop, a unit heater and window shaker would do just fine. Electric wall heaters, unit heaters and baseboards are all relative inexpensive and easy to install.
I am not familiar with any specific requirements for a tack room. Primarily leather storage, right. Would be best to be independent or tied in with the shop.
The apartment is 1300 sf with good construction. "2 tons" of cooling will be enough, but that could be a little light on the heating, so some supplemental heat is recommended.
The installation and the quality/reputation of the installer is more important that the brand of the equipment used. The best installer can make the least expensive equipment work well, and a "hack" can make any manufacturer's best equipment appear to work poorly. I do have a a Trane preference. But again, pick the installer, not the brand.
Given the periodic occupancy, I would recommend basic units only (13 SEER) no high efficiency stuff.
Woodworking
It will be a woodworking shop. Since the tack room will also contain the washer/dryer, we would probably tie it to the upstairs apartment system and take one of the approaches you mentioned for the shop. Although I won't be spraying finishes often, I don't want the duct work in the shop tied to the main living space.
Thanks for your response.
For a woodworking shop you want to think extra hard about dust control and explosion/fire hazards.