Best HVAC for duplex for independent controlls?

20 Replies

What would be the best (cheapest) HVAC system for a duplex conversion type project with the goal of having independent climate controls in each unit? 2 furnaces and 2 AC's? High velocity ductless system? Ducted heatpump system?

Hi Daniel, I actually have an HVAC business and might be able to give you some advice. 

What style of house is it?

Up down duplex?

What is in there currently and how old?

In ground basement or fully above ground? 

I have the same question! I don't mean to hi-jack the OP, but this is exactly what I would like to know moving forward as well.

My situation is an up/down duplex. Each unit is 1,095 sq.ft. 3BR/1B

  • One, 15-20 year old high-efficiency gas furnace.  
  • Air Conditioning - one central air unit.
  • The basement has one baseboard heater as well.

Thanks @Daniel Rosa and @Jaydon H.

Thank you Jaydon and others for your replies!

House is

  • a 2 storey brick house build around 1880's
  • · Basement is stone foundation , unfinished and about 1100 sq ft. Ceiling heingt is about 5’11”
  • · Main floor will be 3 bed 1 bath unit also 1100 sq ft
  • · Second floor will be 4 bed 1 bath also 1100 sq ft.
  • · Existing HVAC is Forced air gas furnace. Ductwors is shared as the house is currently a single family home.

I will be tearing all many interior walls and all the ceiling between the first and second floor units for sound proofing and fire-proofing.

I figured a High velocity system would work if I stuffed 1 unit in the basement and another in the attic. From what I have heard is that they are far too noisy to be practical.







Originally posted by @Jaydon H. :

Hi Daniel, I actually have an HVAC business and might be able to give you some advice. 

What style of house is it?

Up down duplex?

What is in there currently and how old?

In ground basement or fully above ground? 

 

House is:

  • a 2 storey brick house build around 1880's
  • · Basement is stone foundation , unfinished and about 1100 sq ft. Ceiling heingt is about 5’11”
  • · Main floor will be 3 bed 1 bath unit also 1100 sq ft
  • · Second floor will be 4 bed 1 bath also 1100 sq ft.
  • · Existing HVAC is Forced air gas furnace. Ductwors is shared as the house is currently a single family home.

I will be tearing all many interior walls and all the ceiling between the first and second floor units for sound proofing and fire-proofing.

I figured a High velocity system would work if I stuffed 1 unit in the basement and another in the attic. From what I have heard is that they are far too noisy to be practical.

I am also totally willnig to change the ductwork if required.

@Daniel Rosa

In a perfect world you would have one system in the attic and the second system in the basement. High velocity could work but you need the correct ductwork size (installed by someone with HV experience). Depending on your location would depend on wether or not you would want a heat pump because you still need a “backup” heat source wether that is electric or gas. I personally am a fan of high efficiency furnace with AC. Smart thermostat or programmable is always a good idea for energy savings (more important if you are including utilities). Research the HVAC equipment also because brands make a difference.

Originally posted by @Frederick P wallberg :

@Jaydon H.

Attic mount definitely doesn’t work in the majority of Canada.

 It does in BC. Also for a cooling source with a multi level home in any place that gets hot summers, in the attic is a better option being that it is closer to the hottest part in the home. Must be well insulated though. 

Originally posted by @Frederick P wallberg :

@Jaydon H.

The lower mainland makes up less than 1% of Canada’s land mass. Carry on.

I am going to assume you don’t know much about HVAC. That would be news to me that only 1% of Canada has homes with two or more levels AND gets warm in the summer. 

@Jaydon H.

In order to install hvac in an attic, anywhere between approximately Coquitlam to PEI, you’d need to ensure the space was conditioned. Meaning, you’d have to insulate your rafters (spray foam would be easiest). After that, you’d need to ensure your soffit venting was eliminated, along with all roof vents. Then you’d want to budget for providing minimum service to condition that extra “interior” square footage. So you’d be increasing your hvac and ac capacity along with moving it up to your now conditioned attic space. Depending on the age of the home, if you’re dealing with stick built rafters, you would be looking at some fairly significant cost to reinforce to ensure you didn’t get sag that would be cracking your drywall on the ceiling. And then there’s the cost of insulated ducting which isn’t terribly efficient wrt r value.

Without completing all of the above, you’d be looking at significant condensation leading to a mold concern, stains on your ceiling, replacing ceiling and ceiling insulation within a few years.

But please, do elaborate on why in your vast experience and knowledge mounting an hvac system in your attic is a remotely good idea in any part of Canada that experiences winter (below freezing).

The problem with measuring dicks on the internet jordan is that you’ll always find a bigger dick. I’m a power engineer who’s designed, and trouble shooted systems large enough for oilfield facilities. You’re wrong. Carry on.

Originally posted by @Frederick P wallberg :

@Jaydon H.

In order to install hvac in an attic, anywhere between approximately Coquitlam to PEI, you’d need to ensure the space was conditioned. Meaning, you’d have to insulate your rafters (spray foam would be easiest). After that, you’d need to ensure your soffit venting was eliminated, along with all roof vents. Then you’d want to budget for providing minimum service to condition that extra “interior” square footage. So you’d be increasing your hvac and ac capacity along with moving it up to your now conditioned attic space. Depending on the age of the home, if you’re dealing with stick built rafters, you would be looking at some fairly significant cost to reinforce to ensure you didn’t get sag that would be cracking your drywall on the ceiling. And then there’s the cost of insulated ducting which isn’t terribly efficient wrt r value.

Without completing all of the above, you’d be looking at significant condensation leading to a mold concern, stains on your ceiling, replacing ceiling and ceiling insulation within a few years.

But please, do elaborate on why in your vast experience and knowledge mounting an hvac system in your attic is a remotely good idea in any part of Canada that experiences winter (below freezing).

The problem with measuring dicks on the internet jordan is that you’ll always find a bigger dick. I’m a power engineer who’s designed, and trouble shooted systems large enough for oilfield facilities. You’re wrong. Carry on. 

Depending on the age of the home, if you’re dealing with stick built rafters, you would be looking at some fairly significant cost to reinforce to ensure you didn’t get sag that would be cracking your drywall on the ceiling.

🤦🏼‍♂️ Thanks for the laugh. You probably have 1” seismic cable coming down from each corner of your house because your textbook told you to.

Back to the OP, it’s best to talk to your local HVAC contractor in your area and the inspector for your jurisdiction as they will know best. If you would like more information feel free to message me!


“How do you know someone is a power engineer?.... They’ll you.”

   

@Jaydon H.

Power eng don’t really do much of forces along beams etc, mainly fluid and gas dynamics. Though I did teach that stuff long ago. We fall somewhere between sanitation engineer and P Eng. right about beside hvac techs who would install a furnace/ ac setup in an attic @ -20C. Take care.

Originally posted by @Frederick P wallberg :

@Jaydon H.

Power eng don’t really do much of forces along beams etc, mainly fluid and gas dynamics. Though I did teach that stuff long ago. We fall somewhere between sanitation engineer and P Eng. right about beside hvac techs who would install a furnace/ ac setup in an attic @ -20C. Take care.

 

I never once said anything about a furnace in a -20 attic. Excellent attempt at trying to “prove me wrong again” but that was a swing and a miss. Your an angry engineer aren’t you, go for a walk Fred.