[freegem]

I have a tiny home type building with two upstairs lofts and a barn style roof where the peak of the roof is around 12 feet tall.

The building itself is 16' x 34', so 544 sqft total. Under the loft is a 16' x 10' room (160 sqft) that is fully enclosed by a wall.

I need a dual zone mini split heat pump system.

Zone 1 would be the 16x10 room (160 sqft) underneath the loft with a ceiling height of 6 ft 8 in.

Zone 2 would be the entire rest of the house which is 384 sqft (544 - 160 = 384) plus the upstairs lofts.

I live in Texas where summers are consistently 90-100 degrees and winters are pretty mild with random spurts of barely freezing temperatures. The building will be spray foam insulated with open cell spray foam.

Based on my own research I figured Zone 1 (160 sqft) would need an indoor unit around 4000 BTU and Zone 2 (384 sqft plus upstairs lofts) would need an indoor unit around 12000 BTU.

I just wanted to get some feedback to make sure I'm not oversizing or undersizing the system by too much. I've been looking at Daikin since they seem to be a top recommended brand for mini splits, but I was curious if it's worth the extra cost since they're pretty expensive or if the slightly cheaper brands are just as good.

 

[SW Dweller]

Did you do a Manual J?

I would be using closed cell foam, about an R7 per inch.

 

[freegem]

Closed cell is a little out of my price range. It's several thousand dollars more expensive.

Did you do a Manual J?

I didn't know what a Manual J was until I looked it up after your comment. I have not done this. I simply researched how to size a mini split system and then followed some general rules for square footage and BTUs.

 

[user_12345a]

I have a tiny home type building with two upstairs lofts and a barn style roof where the peak of the roof is around 12 feet tall.

The building itself is 16' x 34', so 544 sqft total. Under the loft is a 16' x 10' room (160 sqft) that is fully enclosed by a wall.

I need a dual zone mini split heat pump system.

Zone 1 would be the 16x10 room (160 sqft) underneath the loft with a ceiling height of 6 ft 8 in.

Zone 2 would be the entire rest of the house which is 384 sqft (544 - 160 = 384) plus the upstairs lofts.

I live in Texas where summers are consistently 90-100 degrees and winters are pretty mild with random spurts of barely freezing temperatures. The building will be spray foam insulated with open cell spray foam.

Based on my own research I figured Zone 1 (160 sqft) would need an indoor unit around 4000 BTU and Zone 2 (384 sqft plus upstairs lofts) would need an indoor unit around 12000 BTU.

I just wanted to get some feedback to make sure I'm not oversizing or undersizing the system by too much. I've been looking at Daikin since they seem to be a top recommended brand for mini splits, but I was curious if it's worth the extra cost since they're pretty expensive or if the slightly cheaper brands are just as good.

Most mini-split heads start at 9000 btu but the systems are variable capacity.



You need to do the calculations first and not assume.
In a tiny house, all of those rules of thumb to size - not that they're accurate anyway - go out the window.

HVAC Load Calculation - Maunualj - Whole House Loadcalc

ManualJ load calculator, HVAC calculation, Whole house, - www.loadcalc.net

www.loadcalc.net

 

[heatpump man]

you need to do a Manual J
BetterBuiltNW (en-US)
above website has the free tool. they also have a youtube channel with walk through videos.

I would up getting Mitsibushi Units a 6000BTU 33 seer unit is $900 and a 9000BTU 30.5 seer unit is $1000. Figure another few hundred for wiring supplies. and then the cost of a pro to install or you can try installing yourself if you are handy, many good youtube videos on how it's done.
This is where I am buying my stuff. Surplus City Liquidators
good luck

 

[heatpump man]

it would probabaly be much cheaper to get a single zone 15,000 btu unit and a transfer fan to draw air into the small room. using thermal shutters over windows can also go a long way to keeping the unit warm on the few cold nights you have.

 

[freegem]

That's an interesting idea. I didn't know transfer fans existed. I looked at a few, but I can't tell if they make any with a thermostat that would shut off once the room reaches a certain temperature. That's the main reason for having a separate zone in the smaller room. There will be reptiles in there that require a certain temperature/humidity.

 

[heatpump man]

That's an interesting idea. I didn't know transfer fans existed. I looked at a few, but I can't tell if they make any with a thermostat that would shut off once the room reaches a certain temperature. That's the main reason for having a separate zone in the smaller room. There will be reptiles in there that require a certain temperature/humidity.

probably better off insulating around the reptile homes and using some sort of thermometer based heat lamp to regular temps in just their living space. I met a guy that had a $600 heatinb bill becuase he was raising snakes, hundreds of them and using radient heat.

 

[Missouri Bound]