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Renovating and adding to a 100 year-old home - HVAC - which way to go?

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Joe_A

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Discussion starter · #1 ·
I hope this is an appropriate topic, placed in the correct forum. If not, someone will set me straight, no doubt.

Broad strokes . . .

I own an 1800 square foot home on eastern Long Island which has been completely gutted in preparation for adding 500 square feet to the foundation (basement) and two stacked stories 500 square foot each. The new addition foundation is being poured as I type. The end result will be a new home of 2,800 square feet in keeping with the requirements of the local Architectural Review Board, Zoning Board of Appeals, Building Department, etc. Only the original basement and the "bones" of just part of the original home will remain. All structural approvals are in place,

but . . .

I have no idea yet which way to go concerning the specification of a new HVAC system and I am looking for general "pro and con" advice from professionals here.

Personal Bias:

I have experience with steam systems, hydronic radiant heat and conventional forced air systems.
I do not like forced air systems. My preference is for baseboard hydronic systems for heat.

Previous HVAC?

There was no central AC system.

The home was steam heated, the central component being a Weil-McClain SGO-9 boiler, originally oil-fired but recently converted to gas firing. The old radiators are gone. The builder tells me that I should abandon the 2006 boiler and 2018 burner unit in favor of a more efficient system where ducting can be shared by the H and the AC.

Though I cannot abide conventional forced hot air, the builder tells me that new hot air systems are 95+ % efficient and with modern moisture injection, this is the way to go. I'm told that this would be the least-cost approach as well.

The architect has recommended a boiler in the basement with heating coils and piping to the attic where an air handler will circulate hot air and AC through common ducts. As there are two rental units on the second story a common system with a damper/diverter can be used in the attic. I'm not concerned about splitting utility costs, so I am OK with shared subsystems.

If you have stayed with me thus far, you are probably committed to providing some advice and so thank you in advance!

I'm leaning toward circulated hot and cool air using common ducts.

Question: Is a hybrid hydronic/boiler system actually better than a simpler furnace system to heat the air?

Why do people go through the expense of purchasing a boiler and running piping into the attic as well, if in the end, one is circulating hot air that could just as easily be heated in a plenum chamber?

I have eliminated a heat pump approach for the two second floor units due to hardware and maintenance expense and because electric costs are relatively high in the area. Natural gas is cheaper and already in the building.

I have not completely eliminated baseboard heat from consideration though higher relative acquisition costs may lead me to do so.

Suggestions are welcome

~ Joe
 
Discussion starter · #5 ·
pecmsg said:
OK

I’ve read it all but don’t understand your question?
Click to expand...
My bad, then.

I probably spent too much time on background and not enough on clear request for input.

I'd like to know whether a hybrid hydronic forced hot air system is any better than a conventional hot air furnace system.

And I am open to suggestions as to what professionals would recommend for an HVAC system for my application.

The home is located in the Village of Southampton, New York.

I bought the place in 1981 and am only just now getting around to a major renovation so that I can enjoy it in my twilight years. ;)

Joe
 
#7 ·
.. SOUNDS LIKE You may need 3 OR 4 ZONES.
1. 1,800
2. _ 500
3. _ 500
4. __ ?

OR
System 1, 1 or 2 zones: 1,800 Sq ft
System 2, 2 zones: 500 + 500

Design Temperatures 16'F ____________ Heating Degree Days 5,200
_________________ 88'F DB / 72'F WB _ Cooling Degree Days . 840

______________________________ A/C Operating Time: ~ 700 hours /Year {i.e. ~90 days at 8 hours per day }

Boiler HW heat may be more uniform and efficient based on the use of lower water temperature.
Boiler HW heat would allow for easier control of additional zones.
Additional zones may permit air distribution systems with smaller duct sizing / lengths.

Water temperature would likely be 120'F- 130'F most of the time.
Perhaps ~140'F if ODT < ~ 30'F
 
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#8 ·
Simplifiied ... .:. +/- 33%

ACCA MANUAL J
____ SIMPLIFIED __ As an Initial Thought.

To be THOROUGHLY Verified BY OWNER
__ WITH ROOM-BY-ROOM CALC & PER ZONE

Gmail address: RACINGDAN11
 

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#9 ·
There may be an issue with your plan to share forced air between your rental units. I believe this might be forbidden and that each unit might have to have their own separate air handler. Something to do with preventing the spread of diseases I think. I may be wrong on this, but you should check in to this matter before you get too far in the process.

What is it that you don't like about forced air heating? You mentioned something about "modern moisture injection", so I'm guessing you think forced air is too dry? It is true that steam radiators with vents on them do add some humidity to the air, but between hot water heat and forced air, there should be no difference. I don't see the point of adding a hot water or steam coil to an air handler, unless you are just trying to make use of the boiler that you already own. Forced gas heat would be most efficient, and in the unlikely event that you do need a humidifier, one should be easy to install.

With that being said, I would highly recommend against running boiler pipes to the attic, or putting high efficient furnaces up there unless you are planning on a foaming the roof and making the attic part of the conditioned envelope. You don't want any water pipes in an attic if it's not conditioned, or 90+% efficient furnaces either since they produce condensate that needs to be dealt with.

You might want to un-eleminate heat pumps from the running. If you are going to have air conditioning anyways, heat pumps shouldn't add any more maintenance or other expenses than what you would have anyways with the air conditioners. Mini-split heat pumps might be the way to go.

Or plan on building a mechanical closet in each rental unit in order to stick a small gas furnace in each one, and put the other furnace for your space in the basement. Then it would be easy to add humidifiers if you need them (but I don't think you would since most new construction houses are built tight enough that low humidity doesn't seem to be an issue).

Either way, keep us posted on what direction you decide to go.
 
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Discussion starter · #10 ·
ammoniadog said:
There may be an issue with your plan to share forced air between your rental units. I believe this might be forbidden and that each unit might have to have their own separate air handler. Something to do with preventing the spread of diseases I think. I may be wrong on this, but you should check in to this matter before you get too far in the process.

What is it that you don't like about forced air heating? You mentioned something about "modern moisture injection", so I'm guessing you think forced air is too dry? It is true that steam radiators with vents on them do add some humidity to the air, but between hot water heat and forced air, there should be no difference. I don't see the point of adding a hot water or steam coil to an air handler, unless you are just trying to make use of the boiler that you already own. Forced gas heat would be most efficient, and in the unlikely event that you do need a humidifier, one should be easy to install.

With that being said, I would highly recommend against running boiler pipes to the attic, or putting high efficient furnaces up there unless you are planning on a foaming the roof and making the attic part of the conditioned envelope. You don't want any water pipes in an attic if it's not conditioned, or 90+% efficient furnaces either since they produce condensate that needs to be dealt with.

You might want to un-eleminate heat pumps from the running. If you are going to have air conditioning anyways, heat pumps shouldn't add any more maintenance or other expenses than what you would have anyways with the air conditioners. Mini-split heat pumps might be the way to go.

Or plan on building a mechanical closet in each rental unit in order to stick a small gas furnace in each one, and put the other furnace for your space in the basement. Then it would be easy to add humidifiers if you need them (but I don't think you would since most new construction houses are built tight enough that low humidity doesn't seem to be an issue).

Either way, keep us posted on what direction you decide to go.
Click to expand...

Thanks!

I've had input from my architect and two builders that there is no regulatory or code issue in our area stemming from sharing one HVAC unit with the two rental apartments. Here I am assuming that the return will be in the hallway between the two units. In any case, let's assume that this is not an issue.

I have found forced air to be dry and dusty compared with radiant heat of any kind, but I acknowledge that I am not a professional and I may be simply exhibiting a bias based on experience as perceived. Having experienced dry throat issues and kids bleeding noses. I'll want the RH to be in the 30% plus range.

We are foaming the attic. I assume that there would be no issue with putting an air handler and an evaporator there, but I am guessing the reason for putting heated coils in the attic would be to avoid putting a furnace up there as well. Somehow, I am not comfortable with the idea of flames in the attic.

So . . .

Any other approaches, anyone?

~ Joe
 
#11 ·
Sharing the ducts WILL require fire dampers at every fire proof wall, ceiling, floor penetration.

No reason a gas heater cannot be installed in an attic, just keep the temp above freezing.

Careful with NG, a moratorium on new hookups!

With a full attic and 2 apartments better to have 2 systems.
 
Discussion starter · #12 ·
dan sw fl said:
.. SOUNDS LIKE You may need 3 OR 4 ZONES.
1. 1,800
2. _ 500
3. _ 500
4. __ ?

OR
System 1, 1 or 2 zones: 1,800 Sq ft
System 2, 2 zones: 500 + 500

Design Temperatures 16'F ____________ Heating Degree Days 5,200
_________________ 88'F DB / 72'F WB _ Cooling Degree Days . 840

______________________________ A/C Operating Time: ~ 700 hours /Year {i.e. ~90 days at 8 hours per day }

Boiler HW heat may be more uniform and efficient based on the use of lower water temperature.
Boiler HW heat would allow for easier control of additional zones.
Additional zones may permit air distribution systems with smaller duct sizing / lengths.

Water temperature would likely be 120'F- 130'F most of the time.
Perhaps ~140'F if ODT < ~ 30'F
Click to expand...
Dan,

Thank you for your input as well. I probably have about a month to make my final decision.

Yes, I see that I need at least three zones.

I am going to take your suggestions and that of pecmsg into my discussion with the HVAC guy. I will try and give them equal weight.

The builder I am working with is an easy-going guy who listens to the home-owner and points out freely what his experience has taught him and then he'll do what the home-owner wants so long as it is feasible and will be according to code. The builder has his own HVAC guy and electrician, but he is open to working with others. I'm smart enough not to try to force anyone on him if it looks like their ideas do not meld. I'm giving the builder final say on things of a technical nature.

There is no doubt about one thing, I am biased toward a boiler in the basement and hot water coils there and in the second story attic. That said, the builder asks the question: "What do you think the difference is between air blowing over heated coils versus air blowing over a directly heated chamber? I have to admit, the difference seems negligible.

I do have experience as an end-user of hot air systems and every time they start up, they smell. I have not as yet experienced a hot air system that is not somewhat smelly on start-up at times and is not dusty and dry. Hot water baseboard heat is my first love, with steam heat a close second.

The original system in the house was an old monster of an Ideal Redflash #1 steam boiler and in 2006 I replaced it with the Weill-Mclain Gold Series. But who wants smallish rooms these days with a big steam radiator in each room under a window somewhere?

I suppose with a heated coil hot air approach, the coils will retain some heat after the boiler cycles off - a bit longer than for a plenum chamber. I like the idea of smaller ducts.

Good information as well and thank you.

~ Joe
 
Discussion starter · #13 ·
A bit more information . . .

The 1800 square foot house was uninsulated in the walls. The outside was cedar shingles over tongue and groove and the inside was wire, lath and plaster with only air in between. I had a layer of batting in the attic. Every dollar I spent on that house since 1985 is listed on a spreadsheet. Average heating costs in recent years before the conversion from oil-firing to gas firing was about $2,500 to $2,800.

We are now replacing all the windows with Andersen 400 series, we are foam spraying the attic and insulating the walls inside and out. Even after adding another 1000 square feet of living space, I am told my heating bills will be significantly lower. Time will tell.

There is already gas in the house previously used for cooking, heating and hot water and we haven't shut it off at the street, so we should not be affected by any on-again, off-again moratorium here in New York.

I only converted to gas in 2018 thinking at the time that I'd be keeping the existing boiler, but I was able to project that just converting to gas was going to save $$.

~ Joe
 
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Joe_A
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