Duct, duct, ductless HVAC?

josephny

Can someone please confirm, deny, elaborate or generally set me straight on the analysis between a completely centralized HVAC for a home vs. a ductless system?

Ductless:

1) Attractiveness: I don't really want to see the big white things hanging on my wall -- either high up where I can see them or low down where they'll block furniture. I know the aesthetics have come a long way, and there are in the ceiling units or units that look like art available. While I love technology, I don't want to be a guinea pig. In addition to the dangers of going with state of the art, do they work well?

2) Leading right into this -- Reliability: Seems like a head unit (sorry, what's the correct term) in each of the 7 bedrooms, 5 bathrooms, kitchen, playroom, LR, DR, etc. means an awful lot of moving parts (to break).

3) I would need separate ductwork for an ERV/HRV anyway, so would I be better off with a single network of larger ducts and a centralized HVAC in the basement?

Thank you!

Jamie Hall

I agree with most o your comments on the ductless units. Ugh. However, they do have their place -- and one of the places is to avoid running ductwork.

If you are going to have a heat recovery ventilator system (sensible heat only -- the ones which recover latent heat as well are wonderful of efficiency, but really bad for indoor air quality) -- you will need ample ducts anyway, and the question becomes where -- and how -- can you add adequate ducting. It's easy enough in a new build -- although often as not done -- but as a retrofit it can be challenging.

EdTheHeaterMan

Early on when the ductless was introduced, the benefits were mostly for places where you did not already have ductwork and needed a quiet alternative to a window shaker. Eventually they were the first to grasp the inverter compressor that made the units more efficient by ramping the compressor to the actual need, as opposed to the on-off technology of most other HVAC products.  Today there are many unitary products that employ the inverters to modulate the energy use to that of the actual loss in real time. 

The thing about the central system, you need to purchase the most expensive model in a line to use the inverter (modulating output) technology.  The less expensive models are just the old “Full On or Completely Off” units operating on this inefficient on-off by a thermostat setting logic 

veteransteamhvac

My most popular installs for ductless is garages. Peoples' reactions to what was previously an enclosed but nearly unusable space into a serious extension of their living space is amazing to see. I have one guy building a biplane in his garage now. Even on the coldest winter day or stickiest summer day he can be productive. And needless to say his wife likes getting into a not freezing car in the winter.

josephny

Jamie Hall said:

I agree with most o your comments on the ductless units. Ugh. However, they do have their place -- and one of the places is to avoid running ductwork.

If you are going to have a heat recovery ventilator system (sensible heat only -- the ones which recover latent heat as well are wonderful of efficiency, but really bad for indoor air quality) -- you will need ample ducts anyway, and the question becomes where -- and how -- can you add adequate ducting. It's easy enough in a new build -- although often as not done -- but as a retrofit it can be challenging.

The running of the ductwork itself isn't a problem (just money, right?). The place is gutted and I'm just about done with framing, so, of course, I'm rushing to figure out the next step.

My problem with ducts is my concern with noise, dirt and health.

Does this change your recommendation?

Is the Panasonic Intellibalance ERV a sensible heat ventilator or does the fact that it's an ERV make it fall into a different category?

Thanks.

josephny

EdTheHeaterMan said:

Early on when the ductless was introduced, the benefits were mostly for places where you did not already have ductwork and needed a quiet alternative to a window shaker. Eventually they were the first to grasp the inverter compressor that made the units more efficient by ramping the compressor to the actual need, as opposed to the on-off technology of most other HVAC products.  Today there are many unitary products that employ the inverters to modulate the energy use to that of the actual loss in real time. 

The thing about the central system, you need to purchase the most expensive model in a line to use the inverter (modulating output) technology.  The less expensive models are just the old “Full On or Completely Off” units operating on this inefficient on-off by a thermostat setting logic 

I can't say I know what an inverter compressor is. Sounds like that what make a furnace/boiler modulating.

From what I read, a modulating system is much much much better to have. But, I don't know if it's the heat only or the heat/cooling that modulates. Nor how a modulating system would work in a multi-zoned environment (I have 3 floors to condition).

Thanks.

josephny

veteransteamhvac said:

My most popular installs for ductless is garages. Peoples' reactions to what was previously an enclosed but nearly unusable space into a serious extension of their living space is amazing to see. I have one guy building a biplane in his garage now. Even on the coldest winter day or stickiest summer day he can be productive. And needless to say his wife likes getting into a not freezing car in the winter.

That truly is cool. I love hearing stories of people making other people's lives nicer, especially through the use of expertise and technology.

Thank you.

josephny

I'm sure it's me who is not digesting and understanding everything, but I'm still so confused.

Some options:

1. A single HVAC system that provides heat, AC, ventilation via an HRV or ERV, and humification/dehumidification provided by galvanized ducts; or

2. Hydronic heat AND an centralized AC/ventilation/humidity-control systems w/ducts; or

3. Hydronic heat, AND mini-split ACs (i.e. ductless), duct system (albeit smaller ducts that might not need to go to every room) for an ERV or HRV; or

4. Mini-splits for heat and AC, with an HRV/ERV duct system; or

5. I could just skip the ERV/HRV and use fans for ventilation

I really need to make a decision soon on this.

Thanks!