Bonus room - new construction

[arkansan]

I'm building a new home, 1850 sq ft downstairs with a 350 sq ft bonus room above the garage.

I'm getting ALL kinds of different advice about how to cool it. From a 1 system 5 ton to a two system with 3.5 (downstairs) and 1.5 ton (bonus room).

I'm also hearing that a minisplit ductless system (9000 btu) for the bonus room would be the best option....and a 3.5 ton central system for downstairs.

Any opinions here on what will be the best option?

[heatpumpguru]

In our area the MINIS do not have enough back up heat to cover the load on COLD days,why not a zone system??

[arkansan]

In our area the MINIS do not have enough back up heat to cover the load on COLD days,why not a zone system??

My current thinking is that maybe a zone system is OK if you plan to use the bonus room daily. Otherwise I may be using too big of a unit to cool the lower part of the house when I'm not using the bonus room. For example in a couple of years my kids will be in college and it will just be me and the wife. I doubt that we use the room near as much then.

I'm starting to lean toward a 3.5 central system downstairs and a 1.5 central system upstairs and just forget about it.

Unless someone just swears by the mini ductless as a better option for the bonus room than the 1.5 ton duct system?

[peytonc2682]

minisplits are best used when there is no room for duct. Its hard to say without looking at the house, but I would think that the 2 systems would be best. Judging by your name, I presume that you are from Arkansas which means that heatpumps work great in your area. I recommend a heatpump.

[gonekuku]

Be sure the contractor performs thermal load calculations for the bonus room and the house. You are probably not heating/cooling the garage below the bonus room, so be sure to insulate the floor.

If you insulated the bonus room at R14 in all 6 directions with a few windows, 30% duct loss (attic temp and leaks) you could be as low as .5 tons cooling for that one room. Get stingy on insulation & window efficiency and you could be at 1 ton real fast. If you are using insulation, I am quite certain 1.5 tons for that room would be big overkill.

About a month ago I posted a similar zoning preference question for a two story home. I asked about the PRO's and CONS of 2 units Vs 1 larger unit. In my opinion the collective recommendation was zone with one large unit if you can afford it up front. One large unit means one less unit to purchase, install and service.

Get quotes and ask for themal loads to be calculated using the materials used for your construction.

Zoning and programmable thermostats are great. My household is two humans one dog in 3500 sq ft, Dec 15 to Jan 15 gas bill in Dallas was $120.

[dwiz]

first of all, a load calc will tell you what you need for equipment in the new house. secondly, zone it!
scenario...you get home late one night. walk into the dark house from the garage and hit the light switch. what happens? do all of the lights in the house come on? NO, i hope not. your lighting is zoned. why not heating and cooling too? heat/cool what you want and when you want it, at the temperature you desire. maximize comfort and efficiency. zoning makes for a very comfortable house. and you can do it with less equipment meaning less maintenance down the road.

[arkansan]

first of all, a load calc will tell you what you need for equipment in the new house. secondly, zone it!
scenario...you get home late one night. walk into the dark house from the garage and hit the light switch. what happens? do all of the lights in the house come on? NO, i hope not. your lighting is zoned. why not heating and cooling too? heat/cool what you want and when you want it, at the temperature you desire. maximize comfort and efficiency. zoning makes for a very comfortable house. and you can do it with less equipment meaning less maintenance down the road.

The load calculator says I need 4.5 tons. Two contractors say I should go with a 5 ton, one says a 4 ton is all I need. Is it better to be too high or too low....especially if I zone it?

Also, I can see keeping the thermostat in the bonus room way down when we're not using it...which I expect will only be on the weekends. How does this impact the size of the unit I need?

Is it recommended to zone every room with it's own thermostat or just zone the upper and lower levels?

[BaldLoonie]

So they really did a heat gain calc? 3.5 tons for 1800 sq ft of new construction just seems high to me unless you have a lot of windows or are light on insulation. 5 tons for 2300 sq ft likewise seems big. Be sure they do things right and preferably use 2 stage equipment or you could have some short cycling trying to make a 5 ton unit push air into a small room. If I were doing it, I'd go the 2 systems.

Zoning every room isn't practical, zoning by floor is better. Again, has to be done right. We see too many that aren't :(

[arkansan]

I do have a LOT of big windows as well as 9 and 12 foot ceilings and this is the south so it gets really hot in the summer. I'm using low E windows and fully insulating everything. The guy that did the most extensive calculations recommended 3.5 downstairs and 1.5 ton upstairs above the garage as the best option over a single 5 ton system. I suppose this is probably the safest bet.

However the 4 ton zoned option for the bonus room was about $2000 less. I would sure rather do this if I knew it would work well. Just wish I freakin knew!

[arkansan]

Be sure they do things right and preferably use 2 stage equipment or you could have some short cycling trying to make a 5 ton unit push air into a small room. (

BTW, what do u mean by "2 stage equipment"?

[heatpumpguru]

Put in 2 stage, zoned equipment and you cannot go wrong!!!You also have less compressors and you can only FIRE the tonnage that is needed because you are never in evry zone at the same time calling for HVAC>

[arkansan]

Put in 2 stage, zoned equipment and you cannot go wrong!!!You also have less compressors and you can only FIRE the tonnage that is needed because you are never in evry zone at the same time calling for HVAC>

So I could get by with a 4 ton instead of a 5 ton?

[heatpumpguru]

Maybe the load will tell,but the zoning does help control the load and I think most on site would agree with zone system if it is close the would say go with 4 VS 5 ton system. Also duct work is key with zone system. I do not care what you put in 4 ton or 5 ton,if the ducts suck, it sucks!! SEER is nice but the heart of a GREAT system is the ductwork!!

[mo comfort]

:cool:

Another option would be to install a Ptac HP.

Depending on the zone system and the way the duct system is designed and built, that would be the best way to go. If you really feel that you are not going to use the room after your kids are gone then the only way I would do it is to use 2 stage equipment, but make sure that the equipment is not using 2 compressors to achieve 2 stage.

[arkansan]

:cool:

Another option would be to install a Ptac HP.

Depending on the zone system and the way the duct system is designed and built, that would be the best way to go. If you really feel that you are not going to use the room after your kids are gone then the only way I would do it is to use 2 stage equipment, but make sure that the equipment is not using 2 compressors to achieve 2 stage.



Hey I'm not a HVAC guy. Could someone please tell me what "2 stage" equipment is?

[dash]

The compressor operates at two stages low and high capacity.

Low could be 50 or 70% of high depending on the brand and model.

Advantage for zoning is ,when only one zone is calling for cooling,it can usually run in low,so you don't have 5 tons of air to deal with,could be just 2.5 tons.

The best in zoning is the Carrier Infinity Two Stage,no bypass damper needed or allowed,IMHO.

Check it out very nice syatem.

[Chuck 999]

Ptac unit is the best and the most cost and effctive way of treating a bonus room... especially in the summer monthes, fairly innexpensive and will take care of all seasons.

[jbac]

go with a separate system for bonus room.

[jbac]

ton and a half is probably oversized for your bonus room.but if you go with zone damper,even with 2 stage 4 or 5 ton will be more oversized with first stage at 50 or 70% with a call for bonus room only.also may seriously consider heat pumps.use 2 stage heat 2 stage cool for main house & 2tage heat for bonus.trane used to manufacture a 1 ton split system.may be worth looking into.go with separate systems regardless. i do it all the time in tennessee and it works well.