New construction - Central AC V Ductless Units

[Angel0802]

I am a home owner and building a new home in Queens, NYC.

The house will be 2 floors, each approx 1,000 sq feet and the cellar which will also be approx 1,000 sq feet. I will spray foam insulation on the exterior walls. Use R18 or better in the attic. For heat, my plumber will be installing radiant heat throughout the house. I am really confused on what to do with cooling.

For cooling I am either doing Central AC or Ductless Units throughout the house. Is one better than the other?

My electrician told me, ductless units are more efficient. My wife and I do not mind having a ductless unit in each room (it isn't an eye sore for us).

I talked to a few HVAC contractors and I havn't gotten a clear answer, I feel that a contractor will push with what he wants. I talked to about 5 contractors and 3 went with Central AC and 2 suggested ductless. Cost isn't as much as a factor, I just want to do the right thing and not worry about my house not being properly cooled in the summer.

Thoughts?

[vstech]

please better define the R18 in your attic... are you foaming the roof framing, or putting fiberglass batts in the rafters??? I'm just curious what your plans were.

as for ductless, they have advantages over central air, but exact sizing can be an issue. the nice thing about them is they take less space in the design of the house than ductwork.

[Tommy knocker]

6 of one half dozen of the other. Your the factor. Ductless gives better and more convient control since you can customize each area. Central gives, in most cases, lower front end cost, less moving parts and lower collateral damage risk if condensate drain clogs up. You can zone a central system and get close on the control issue to the ductless. Both will do the job for you. My personal opinion if it were mine? Central With the ductless you basically are putting a small air handler and evap coil in every room and with that all the parts associated with them. The more parts the more potential for part failure and just because they are smaller don't mean they are cheeper. IMHO. Good luck.

[jtrammel]

If cost isnt too much of a factor look into vrf (variable refrigerant flow) mini splits daikan, mitsubishi, Samsung, johnson controls all make them. They are super efficient and quiet. You can have ducted and ductless indoor units and on some models. These types of units are where the hvac industry is headed IMO, especially in urban areas where space is limited. Good luck and know that you can put the most efficient, cutting edge top dollar piece of eqipment in but if it is not sized and installed properly you will have problems, so choose a good contractor to work with

[Angel0802]

please better define the R18 in your attic... are you foaming the roof framing, or putting fiberglass batts in the rafters??? I'm just curious what your plans were.

as for ductless, they have advantages over central air, but exact sizing can be an issue. the nice thing about them is they take less space in the design of the house than ductwork.

I am either going to spray the foam (like the exterior walls) or place fiberglass in rafters. This is another one of those, it depends which contractor you ask. I will probably go with the open cell spray foam stuff everywhere so the house can breathe but regardless, I plan to insulate the house the best I can.

I am worried, if I choose ductless I will regret it down the line. I have done some research on the pros and cons of the ductless and I have yet to see a reason not to go this route other than upfront cost and the potential higher repair costs. I really like the idea of having individual control or zones.

As I said, upfront cost isn't so much a factor. My walls are open so now is the time to make a decision and live with it forever.

[jtrammel]

Go with variable drive mini splits, you won't regret it

[t527ed]

if it were mine i would go with the zoned central unit.
install costs would be cheaper, quieter, less parts to go bad, and better air filtration with a good media filter.

in the long run ductless may also hurt your resale value, not everyone like the unit hanging on the wall look.

[BaldLoonie]

Foam the roof deck. I'd put a small AH in the attic for the 2nd floor and 1 in the basement for 1st and basement. Could zone that.

Next buyer may not like the idea of the mini split or VRF wall units everywhere. VRF units sound great but what about reliability and tech who know how to work on it? I'd hate to be paying out of warranty repairs.

[catmanacman]

I would also go convetional system as i have not ran across any 15 year old mini splits .i am not convinced of the long term durability of them

[motoguy128]

Foam the roof deck. I'd put a small AH in the attic for the 2nd floor and 1 in the basement for 1st and basement. Could zone that.

Next buyer may not like the idea of the mini split or VRF wall units everywhere. VRF units sound great but what about reliability and tech who know how to work on it? I'd hate to be paying out of warranty repairs.

+1. 2 systems. Make sure they get sized correctly. I'd put my money that you only need 1.5 tons for each floor. Your home will be tight, so you'll want a HRV for fresh air and dehumidification in the winter. IF you can, install the HRV with the exhausts in the bathrooms and kitchen and supply to both systems.

If you entertain a lot and put in a sizeable kitchen vent hood you might consider a 2 stage unit downstairs since in smaller homes, temperatures can spike pretty quick with guests and cooking.

You'll need minimal conditining in the basement, unless you fully finish it and plan to entertain. IF you do, then zone it.

[skibme]

Do you have a plan in mind should you decide to go with ductwork? Kneewalls,soffits,chases... How about your electrical service?

[Angel0802]

Foam the roof deck. I'd put a small AH in the attic for the 2nd floor and 1 in the basement for 1st and basement. Could zone that.

Next buyer may not like the idea of the mini split or VRF wall units everywhere. VRF units sound great but what about reliability and tech who know how to work on it? I'd hate to be paying out of warranty repairs.

One of the HVAC contractors that spec'ed Central AC, told me I should put 1 AH in the attic and wanted to use Carrier Infiniti FE4A (4 ton unit) for the entire house. He said you can make 2 zones with this unit.

Does this sound right? Would 2 seperate AH's be better?

He was the HVAC contractor I trusted the most because he sounded like he know alot. I use the word sounded, because I am not a HVAC expert by any means but he spoke like he knew what he was talking about. He was also the most expensive, but not by much.

[Angel0802]

Do you have a plan in mind should you decide to go with ductwork? Kneewalls,soffits,chases... How about your electrical service?

My house currently has 150AMP service and my electrician and locality cleared me for central AC.

As far as the ductwork, I was going to sit with the HVAC contractor when I decide which route to go with and plan this. I have closets in pretty good places so I think the ductwork will be smooth.

[motoguy128]

One of the HVAC contractors that spec'ed Central AC, told me I should put 1 AH in the attic and wanted to use Carrier Infiniti FE4A (4 ton unit) for the entire house. He said you can make 2 zones with this unit.

Does this sound right? Would 2 seperate AH's be better?

He was the HVAC contractor I trusted the most because he sounded like he know alot. I use the word sounded, because I am not a HVAC expert by any means but he spoke like he knew what he was talking about. He was also the most expensive, but not by much.

Infinty zoning is probably one of the best systems out there. Its' modulating and you could even zone each bedroom space and also zone the basement as well as different parts of the downstairs if the useage or occupany varies. I question if you need 4 tons, especially if zoned. I bet with spray foam throguhout a load calculation will say 3 tons is plenty. You're only in Queens, not South Florida or Texas. You summer design temeprature isn't that high and humidity is moderate. WIth zoning you can actually undersize slightly and take advantage of even longer run times since all zones are rarely occupied during peak periods.

However, with zoning, ductwork sizing and layout is even more critical.

[Tommy knocker]

One of the HVAC contractors that spec'ed Central AC, told me I should put 1 AH in the attic and wanted to use Carrier Infiniti FE4A (4 ton unit) for the entire house. He said you can make 2 zones with this unit.

Does this sound right? Would 2 seperate AH's be better?

He was the HVAC contractor I trusted the most because he sounded like he know alot. I use the word sounded, because I am not a HVAC expert by any means but he spoke like he knew what he was talking about. He was also the most expensive, but not by much.

Good system. Tonnage is at the high end of good, you'll get alot of different opinions that, but 500sqft per ton is ok. A 3 or 3 1/2 ton will work with better dehumidification but on a 95 degree day may not shut off and struggle to maintain set point. If you are planning to use and condition the basement I would stick with 4 tons, won't need much cooling down there but may add to much for the 3 or 3 1/2 ton.

[motoguy128]

Good system. Tonnage is at the high end of good, you'll get alot of different opinions that, but 500sqft per ton is ok. A 3 or 3 1/2 ton will work with better dehumidification but on a 95 degree day may not shut off and struggle to maintain set point. If you are planning to use and condition the basement I would stick with 4 tons, won't need much cooling down there but may add to much for the 3 or 3 1/2 ton.

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

[Angel0802]

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

Although temperatures aren't that high here in NYC, the humidity kills. Don't know if that affects the tonnage or not.

I should add that my cellar (7.5' ceilings) is fully finished and will be occupied alot. We have the main TV area there and an entrance to the outside. Although, it stays pretty cool compared to the rest of the house and this is pre-renovation, and we will insulate it even better during construction.

I think I am leaning towards a central zoned Infiniti system. I will double check with the HVAC contractor about the tonnage.

Other contractors who did not recommend the Infiniti (actually talked bad about it, being a waste of money) wanted to put 2 AH units, 1 3 ton for cellar and main floor and 1 2 ton for bedrooms.

[motoguy128]

Although temperatures aren't that high here in NYC, the humidity kills. Don't know if that affects the tonnage or not.

I should add that my cellar (7.5' ceilings) is fully finished and will be occupied alot. We have the main TV area there and an entrance to the outside. Although, it stays pretty cool compared to the rest of the house and this is pre-renovation, and we will insulate it even better during construction.

I think I am leaning towards a central zoned Infiniti system. I will double check with the HVAC contractor about the tonnage.

Other contractors who did not recommend the Infiniti (actually talked bad about it, being a waste of money) wanted to put 2 AH units, 1 3 ton for cellar and main floor and 1 2 ton for bedrooms.

THe design dewpoint is fairly high considering the moderate dry bulb design temperature. Its 'a 73F Dewpoint. But still not as high as 75-77F in more humid parts of the contry. That does affect your load, but I think you still wouldn't need 4 tons in that space unless air leakage is very high . Being new construction, it should be fairly good. Plus, if humidity is the concern, then yet again, oversizing will only make it worse. You don't want it be in low stage 90% of the time where you have a lower latent ratio. Properly sized, you'd should be in low stage around maybe 2/3rds of the run time through the whole season.

[Angel0802]

THe design dewpoint is fairly high considering the moderate dry bulb design temperature. Its 'a 73F Dewpoint. But still not as high as 75-77F in more humid parts of the contry. That does affect your load, but I think you still wouldn't need 4 tons in that space unless air leakage is very high . Being new construction, it should be fairly good. Plus, if humidity is the concern, then yet again, oversizing will only make it worse. You don't want it be in low stage 90% of the time where you have a lower latent ratio. Properly sized, you'd should be in low stage around maybe 2/3rds of the run time through the whole season.

Thanks for the insight. I will ask him what he feels about going with a 3.5 ton unit.

A

[ga-hvac-tech]

If cost isnt too much of a factor look into vrf (variable refrigerant flow) mini splits daikan, mitsubishi, Samsung, johnson controls all make them. They are super efficient and quiet. You can have ducted and ductless indoor units and on some models. These types of units are where the hvac industry is headed IMO, especially in urban areas where space is limited. Good luck and know that you can put the most efficient, cutting edge top dollar piece of eqipment in but if it is not sized and installed properly you will have problems, so choose a good contractor to work with

Agree with this post... including get a competent contractor (actually the competent contractor is the MOST important part). Drains for each mini head (part you see in each room) is important also.
The multi-head systems have come a LONG way in recent years; they are quiet and comfortable.

I would shop lots of contractors installing Daiken and Mitsubishi. Fujitsu is a good co, however lately they are having issues.