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HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrlynn
Date: January 03, 2018 11:10PM
Number Two Son Nathan bought a '70s-era house in the Boston area (Dedham, MA), that turns out to need a lot of work: leaks and moldy insulation throughout. He's had to have all the exterior walls and some ceilings gutted, which revealed all manner of framing and electrical and plumbing problems as well. It's a nightmare; he and his family (all seven of them) are staying with us until the work is done.

In the process of gutting the walls, the hot-water baseboard heaters, running from a natural-gas furnace, have either been damaged, or revealed to have problems. So he's trying to decide whether to replace the baseboard heat (plus a couple of large but marginally-adequate ductless AC units). An HVAC guy has recommended he install ducts and two new hot-air furnaces, one in the basement for that and the first floor, and one in the attic for the second floor and attic. Plus he would install external AC compressors to use the same ductwork.

Since all the insulation has been pulled out of the exterior walls, running the ducts will not be a problem. The costs are comparable, though the HVAC guy, surprisingly, is quoting more for renovating the hot-water system. Maybe because if they want AC, it would still make sense to install ducts.

I never heard of running two furnaces in different floors, but my experience is decades out of date. Is this now common? Does it make sense? And if he goes that route, which brand systems should he look at?

Any observations or links welcome. Personally, I don't like hot-air heat, nor AC, but it ain't my house.

/Mr Lynn



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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: JoeH
Date: January 03, 2018 11:30PM
Two smaller furnaces can simplify the running of ductwork and provide a simple zoned system for forced hot air as compared to one furnace in the basement for the whole house. The main advantage of forced hot air is the relative ease of adding central air conditioning to the ductwork.

For comfort I personally would recommend radiant heat. It can easily be set up for zoned heat, and running small diameter piping can be less intrusive than ductwork.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: MikeF
Date: January 04, 2018 12:03AM
Our house in Southern California has two HVAC systems in the attic -- one for the first floor and one for the second floor. Two separate thermostats.

Edit: Ducted forced air heating and cooling... And really came in handy in the summer when one of the A/C units failed -- kept the house reasonable until it could be repaired...



Edited 1 time(s). Last edit at 01/04/2018 12:07AM by MikeF.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: billb
Date: January 04, 2018 12:13AM
Every hot air system I've known was loud and fraught with drafts and airborne dust aggravating some with allergies.

I'd rather have hydronic heat and mini-split Air.

I'm gonna assume the existing system is original to the house and needs replacing.
I'd get another opinion/estimate from someone else.
Replacing everything seems absurd.

[thevillageplumber.com]



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Cary
Date: January 04, 2018 07:05AM
I have a high ranch with a hot water boiler and 2 air handlers with heat and AC. It works, but it's not the most comfortable heat (or AC).

Generally, hydronic heating is the best. Radiant floor heat is great, but retrofitting can be expensive, and difficult. Baseboard heating works week, is affordable, but most people don't like the looks.

As recommended, I'd get 2nd and 3rd opinions.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrlynn
Date: January 04, 2018 07:28AM
Bill, Nathan's house is c. 2,500 sq ft, plus c. 500 sq ft in attic, which he plans to spray-foam insulate and use as additional living space. He's not sure the ductless 'mini-split' AC would be adequate; the HVAC guy he talked to said he doesn't do ductless AC. A complete ducted heat/AC new would be about $18,000.

His plumber said replacing the baseboard pipes (original from 1966—not '70s, as I said) would cost c. $6,000. New ductless with four heads might cost c. $8,000.

Some people seem to think filtered hot air is less allergenic than the dust that collects in baseboard vanes. I have no clue (but we never clean ours—probably should?).

By 'hydronic' do you mean hot water?

/Mr Lynn
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: testcase
Date: January 04, 2018 08:15AM
Has he considered in-wall cast iron radiators? My 1890’s house had MASSIVE cast iron units that I had changed to in-wall units during a renovation. I also went from a single zone, “gravity feed” system to a two zone system with circulator pumps. The in-wall units are MUCH smaller. I LOVE this system! SUPER quiet (my experience with the slant fin systems is, because of their low mass, they cycle on and off every 10 minutes or so). Once heat is called for, the circulators have the rooms at the temperature I’ve set in ~ 10-20 minutes (I have 11 rooms). The furnace then shuts off and, it’s a long time before it needs to come back on. I too have natural gas so, I was able to get a super-high efficiency cast iron boiler. This investment will last for decades so, you won’t need to upgrade again for a LONG time (and then, you’d only be looking to replace the boiler. I would also recommend your son looks at “on-demand water heaters instead of the “standard” units.

I believe the big advantage to a forced air system is that you can “handle” the air (hear, cool humidify/dehumify filter etc). Air systems are often noisier too.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrbigstuff
Date: January 04, 2018 09:06AM
man, I wish I had cast iron baseboard radiators again, I loved those in one house we rented for a while. in-wall must be pretty good, too, I imagine. even upright standalone radiators would be good. I have FHW baseboard now and I don't like it. not about to change it because of $$$$ but I would prefer something else. my Victorian era house still has some of the heat registers and I am keeping them around just in case I come into a windfall of money and could do something like a newfangled condensing system.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: FormerlySaleenl
Date: January 04, 2018 09:08AM
I have had a mix of all of the above and prefer baseboard heating, hands down. In my experience, it is less dusty, more even, less dry in the winter, and quieter than forced air. Even if it cost a bit more, I would opt for it in a heartbeat.

My favorite combo was a house with baseboard heat and forced air ducts for AC. Mini-splits are nice but a bit of an eyesore, kinda loud, and likely very uneven over a house of 2500 sq ft. We've had two mini-splits over the years and one had a coil crack after 3 years and the repair cost was almost the same as replacing the whole system. The HVAC company gave us a decent deal on the replacement but it was frustrating.

Our current 1923 house had its radiators removed before we moved in, sadly. We have two furnaces- one in the basement and one in the attic - because it was easier to run the ductwork that way. The setup works ok but there are a few things that we didn't anticipate.

I don't think the attic furnace will last as long because it is in an unconditioned space and operates in very cold and hot conditions. On top of that, the attic furnace is a pain to service, because we have pull-down stairs. Both these things might not be an issue for your son, though.

We cannot install a humidifier on the attic furnace because of the very low temperatures and lack of water/drain lines. We can't seem to get the upstairs humidity above 35% during the winter, despite running multiple small humidifiers. The humidifier on our downstairs system maintains around 40% humidity and we don't have to constantly refill humidifiers.

The blowing air noises of the upstairs furnace are also *very* loud. We were told it was because of its location but also because it is a high-efficiency model and they have stronger blowers than older ones.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: vicrock
Date: January 04, 2018 09:35AM
When we built this house we opted for radiant underfloor heat - and love it - we have 6 zones so it is easy to get the heat you want where you want it.

If you want whole house AC, then ducted forced air will be more economical - but we have no need of ac.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: billb
Date: January 04, 2018 09:48AM
Quote
mrlynn

By 'hydronic' do you mean hot water?

/Mr Lynn

Yes, and cast iron baseboard is the way to go if you can afford it. No fin tinking and copper pipe expansion noises of aluminum finned copper pipe. The cast iron is heat retaining mass and the larger reservoirs of water help minimize room temp swings.



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 04, 2018 03:28PM
Quote
billb
Every hot air system I've known was loud and fraught with drafts and airborne dust aggravating some with allergies.


In Atlanta A/C is at least as important as heat. We have two forced-air systems, one for the main floor and basement, and one for the second floor. We also have a really good HVAC contractor, who I have now worked with for 30 years.

Thoughts on forced air systems:

1. Fresh air makeup is a really good idea, especially if the house will be newly insulated.
Our system brings in 8% fresh air from a duct run to the front of the house. We do not have an air-to-air heat/cooling exchanger, but these do exist. When the air is on, the house is lightly pressurized, which keeps pollen from coming in, for example, and pushes pollutants out. This helps with outgassing from products like new plywood, particleboard and carpet.

2. Interlining (adding insulation to the inside of ducts), especially for the big ducts, keeps the system quiet.
This was one tip from our HVAC contractor when we did our big renovation 30 years ago.
Our main system is dead quiet. We can hear the upstairs air handler fan when its on from the room it's in, but that's because it's just behind a closet door. Otherwise we don't hear it.
No creaks or pops, and no sound carrying from one room to another. This, and return ducts in each room, are what make our HVAC quiet.

3. Good filters keep dust down.
We have a HEPA quality filter on the main system, with a 2" prefilter. The upstairs has a smaller, but still effective "SpaceGuard" filter.

4. Add humidification for the winter
Aprilaire humidifiers have worked well for us.

5. Make sure ducts are pressure checked and leaks thoroughly taped before they are insulated.

6. Avoid flexible ductwork as much as possible.
Contractors like flexible ductwork because it's easy to install. But it's not as durable, and I don't think air flows through it as well. We've got some, but not much.

7. Ask how much more a condensing furnace would be.
Condensing furnaces don't need a metal chimney for exhaust (they use a PVC pipe which can run horizontally) and run at very high efficiency, but are more expensive.

8. This should be basic, but:
- Supply ducts next to areas of heat or cooling loss - such as below or above windows.
- Return ducts in the center of the house.
- Having return ducts in each room will add to comfort and make the system quieter, but takes more ductwork.


Good luck.

- Winston



------------------------
Be seeing you.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: billb
Date: January 04, 2018 08:18PM
Quote
Winston
Quote
billb
Every hot air system I've known was loud and fraught with drafts and airborne dust aggravating some with allergies.


In Atlanta A/C is at least as important as heat. We have two forced-air systems, one for the main floor and basement, and one for the second floor. We also have a really good HVAC contractor, who I have now worked with for 30 years.

Thoughts on forced air systems:

1. Fresh air makeup is a really good idea, especially if the house will be newly insulated.
Our system brings in 8% fresh air from a duct run to the front of the house. We do not have an air-to-air heat/cooling exchanger, but these do exist. When the air is on, the house is lightly pressurized, which keeps pollen from coming in, for example, and pushes pollutants out. This helps with outgassing from products like new plywood, particleboard and carpet.

2. Interlining (adding insulation to the inside of ducts), especially for the big ducts, keeps the system quiet.
This was one tip from our HVAC contractor when we did our big renovation 30 years ago.
Our main system is dead quiet. We can hear the upstairs air handler fan when its on from the room it's in, but that's because it's just behind a closet door. Otherwise we don't hear it.
No creaks or pops, and no sound carrying from one room to another. This, and return ducts in each room, are what make our HVAC quiet.

3. Good filters keep dust down.
We have a HEPA quality filter on the main system, with a 2" prefilter. The upstairs has a smaller, but still effective "SpaceGuard" filter.

4. Add humidification for the winter
Aprilaire humidifiers have worked well for us.

5. Make sure ducts are pressure checked and leaks thoroughly taped before they are insulated.

6. Avoid flexible ductwork as much as possible.
Contractors like flexible ductwork because it's easy to install. But it's not as durable, and I don't think air flows through it as well. We've got some, but not much.

7. Ask how much more a condensing furnace would be.
Condensing furnaces don't need a metal chimney for exhaust (they use a PVC pipe which can run horizontally) and run at very high efficiency, but are more expensive.

8. This should be basic, but:
- Supply ducts next to areas of heat or cooling loss - such as below or above windows.
- Return ducts in the center of the house.
- Having return ducts in each room will add to comfort and make the system quieter, but takes more ductwork.


Good luck.

- Winston

which is why I wrote hot air system
Dedham is in Massachusetts I think



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
BOYCOTT YOPLAIT [www.noyoplait.com]
[soundcloud.com]




Edited 1 time(s). Last edit at 01/04/2018 08:20PM by billb.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 04, 2018 08:54PM
Quote
billb
which is why I wrote hot air system
Dedham is in Massachusetts I think

Could you clarify? Everything I wrote applies equally to a forced air system which only has a furnace and no A/C. I was trying to show that a forced air system could be quiet, comfortable, and actually reduce the amount of dust in the house, as my experience differs from what you'd stated.

My comment about Atlanta was because forced air systems are pretty much all you see here, due to the need for A/C. mrlynn asked about "ducted hot air", so I was trying to give some info based on my experience with such a system.

The "hot air (only) systems" (such as at my mother's summer place in Michigan) I've seen have the same kind of air handler as with full HVAC systems, and can have an A/C chiller added to them if desired.
Well, not quite: the hot air system we had in MI when I was a child used a firebox where you built a wood fire, and worked on gravity, so wasn't "forced air". Maybe gravity air based systems are sold in Massachusetts. Don't think you can use filters with a gravity system, and I don't know about condensing gravity systems. But the other comments all apply.

Our system in Atlanta uses natural gas for heat, and the one in MI uses propane. Many in Atlanta have heat pumps, which probably are not even sold in Massachusetts. I'd guess there are forced air heating systems which can use fuel oil as well. I don't know if condensing furnaces exist which use fuel oil, but I don't know of a reason they couldn't exist.


Good luck.

- Winston


ps: High efficiency fireplaces or wood or pellet stoves are forms of gravity heating systems. But I don't think they are considered "ducted hot air".



------------------------
Be seeing you.



Edited 4 time(s). Last edit at 01/04/2018 08:59PM by Winston.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrlynn
Date: January 04, 2018 10:58PM
Yes, I'm a little confused, too. I was assuming 'hot air system' was the same as 'ducted hot air' and also the same as 'forced air system'.

BTW Winston, Nathan tells me the HVAC guy he was talking to said insulating the inside of the ducts is a bad idea, as can lead to mold growth. He says you should insulate the outside of the ducts.


/Mr Lynn
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: FormerlySaleenl
Date: January 05, 2018 08:24AM
Did your son get a Mass Save evaluation done? That can lead to rebates on insulation and hvac equipment. [www.masssave.com]

Also - fun fact - heat pumps are sold in Massachusetts! Our neighbors did a renovation and put in two but they are installed on platforms to keep them above the snow in the winter. We had one when we lived in St. Louis, but opted for traditional furnaces/AC units when we moved to Mass. Now I'm curious if our neighbors have backup heat and, if not, how they have fared given the low temps over the past two weeks.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: JoeH
Date: January 05, 2018 09:32AM
All heat pump installations in MA will have some kind of backup heat. Most common is resistance heat coils in the unit itself to kick in during cold weather. When the resistance heat kicks in will depend on the size and configuration of the heat pump. Instead of resistance heat some people opt for a separate heat source fueled by natural gas, propane, fuel oil or wood. More expensive is a heat pump installation utilizing a buried loop of tubing circulating water for a geothermal heat pump.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 05, 2018 12:45PM
Quote
mrlynn
Yes, I'm a little confused, too. I was assuming 'hot air system' was the same as 'ducted hot air' and also the same as 'forced air system'.

BTW Winston, Nathan tells me the HVAC guy he was talking to said insulating the inside of the ducts is a bad idea, as can lead to mold growth. He says you should insulate the outside of the ducts.


/Mr Lynn


I'll have to ask my HVAC guy what he used for insulating the inside of the ducts. My vague memory from 30 years ago was that it was fairly firm sheets of 3/4" fiberglass, with dark coating on inner (open to the air in the duct) side which may have been plasticized. It's what is used in commercial HVAC systems. As I mentioned, it was only used on the largest ducts right near the furnace.

All ductwork needs outside insulation to prevent heat or cooling loss before the air gets where it's intended. That was part of my point about doing a pressure check and sealing any leaks before the ducts are insulated. In the case of cooling, it also prevents condensation on the ductwork, which can then cause mold to form (but on the outside of the ducts, not the inside). Properly done insulation is critical for this, especially in spaces which are not conditioned, like attics, crawl spaces, and garages.

For a heat-only system I can't see how mold would form, as the heat itself would keep the ducts dry, even with a humidifier in the system.

For cooling, the reason we call it "air conditioning" instead is because the chiller acts as a dehumidifier, drying the air. Mold in the ducts should not be a problem. Note that A/C systems must be left on the "auto" setting for the fan. This gives the chiller a chance to drain and dry out, as the fan goes off when the compressor goes off. If the fan runs when the A/C is not active the moisture that the chiller condensed will evaporate and go back into the air - this could cause mold, but will at least partly defeat the "conditioning" part of cooling.

Coincidentally, we had a major mold problem in our basement last year, caused by a drain backup (luckily only rainwater). We ended up doing extensive work on our HVAC system, including replacing all the insulation on the outside of the ducts. There were never any problems with mold inside the ducts, with the exception of the boot (where the register attaches to the duct) on one duct which was affected by the basement mold and which was not properly insulated. This was on a 29 year-old duct system in Atlanta, which gets LOTS of humidity. We do sometimes get mold on the outside of registers due to condensation, but that's it.


If the ducts are going to get moldy inside, I'd guess that will happen regardless of whether they have inside insulation. Mold can form on metal or plastic as well as on insulation. If the HVAC contractor Nathan is using has had problems with mold in duct systems he's designed, then he's not doing it right. If the air moves too slowly the ducts will get too cold, which can cause condensation. Not sealing the ductwork and insulating it properly (on the outside) can also cause mold problems, but more on the outside of the ductwork than the inside (since leaking cold air causes condenation).*

There is some science to designing a proper duct system for air conditioning. It would not surprise me if many HVAC contractors in New England are not proficient at this. Many HVAC contractors in Atlanta can't do it properly either, and every system they install has air conditioning.


Good luck.

- Winston


* This is based on 30 years' experience as a homeowner in Atlanta, and on extensive conversations with two different competent HVAC contractors last year when we had the basement mold problem. We ended up replacing our main HVAC system with a variable speed system, and installing a new electronically controlled variable damper system with 5 zones to replace a previous electro-mechanical 6 zone system.



------------------------
Be seeing you.



Edited 2 time(s). Last edit at 01/05/2018 12:51PM by Winston.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 05, 2018 01:03PM
Quote
JoeH
All heat pump installations in MA will have some kind of backup heat. Most common is resistance heat coils in the unit itself to kick in during cold weather. When the resistance heat kicks in will depend on the size and configuration of the heat pump. Instead of resistance heat some people opt for a separate heat source fueled by natural gas, propane, fuel oil or wood. More expensive is a heat pump installation utilizing a buried loop of tubing circulating water for a geothermal heat pump.


Air based heat pump systems in Atlanta also have backup heat, almost always via electric resistance heating. The backup is needed if it goes much below about 25 degrees. Surprised anyone would use the electric resistance backup heat in MA, as it's the most expensive way to heat.

Geothermal systems all use heat pumps. Expensive to install (mainly due to drilling for the geothermal loop), but cheap to run. However, based on my sister's experience with a now about 10 year old system, geothermal systems are more fragile than traditional furnaces. They have more parts which can break: pumps for the working fluid for the geothermal loop, and the compressor part of the system which runs almost year-round. The A/C compressors on our HVAC system have required the most maintenance of any part of the system. Heat pumps use the same kind of compressor, and just run backwards for heating.

Geothermal systems don't need a backup heat source as air based heat pumps do.

Good luck.

- Winston



------------------------
Be seeing you.



Edited 1 time(s). Last edit at 01/05/2018 01:03PM by Winston.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: JoeH
Date: January 05, 2018 01:54PM
There are a lot of "all-electric" houses here in the Northeast, most built during the period from the '50's to the late '70's. Electricity from coal or oil fired generating plants was relatively cheap, and the price of electricity was being touted as going to be even cheaper from the nuclear plants being constructed. The OPEC oil embargo ended the source of cheap oil, retrofitting coal plants to meet pollution reduction targets was expensive, and for a number of reasons nuclear sourced electricity did not stay cheap.

Initially all of these houses would have been fitted out with electric baseboard units for heating. Some owners have since installed other methods of heating them, but many just went the route of improving the insulation. For those that stayed all-electric, that was adding heat pumps of one sort or another.

Here the geothermal heat pump installations may still require supplemental heat to keep up on the coldest days. Again this would depend on the design of the system and the trade offs made. For instance, a system large enough to keep the house warm down to 10 degrees would be less expensive enough compared to one able to do so down to -15 or -20 that it makes economic sense to use that with some supplemental heat.
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 05, 2018 02:53PM
What you say about the northeast and sizing of geothermal systems vs. supplemental heat makes sense. I think in Atlanta that's not an issue, but I could be wrong. When I priced geothermal for our house my impression was we would not need supplemental heat, and I'm sure my sister doesn't have it. But all the air-based heat-pump systems I've seen do.

A really cold night in Atlanta might be 18º. It has gotten colder on occasion, but very rarely.

Lowest temps recorded in Atlanta:
[patch.com]
-9 degrees, Feb. 13, 1899
-8, Jan. 21, 1985
-6, Jan. 20, 1985
-5, Jan. 11, 1982
-3, Jan. 30. 1966
-3, Jan. 24, 1963
-2, Jan. 10, 1982
-1, Jan. 6, 1884
0, Dec. 25, 1983
0, Jan. 17, 1982


- W



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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrlynn
Date: January 05, 2018 03:47PM
UPDATE: Looks like Nathan is going to go with the forced-hot-air-plus-AC option, for various reasons, including the age of the older systems and the ability to run new ducts while the walls are open. He plans to keep the old boiler, as it's apparently tied to a hot-water tank.

Thanks to everyone for the comments and advice. I have suggested that he talk about Winston's observations re sealing and insulation with his HVAC contractor.

Re heat pumps: My daughter and her family have a heat-pump system in Virginia. It has a subsidiary electric heating element, but that is not working, so with the cold spell the HP is not keeping up. They're supplementing it with their wood stove. Fortunately, they live in the woods, so there is no shortage of firewood.

/Mr Lynn
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: mrlynn
Date: January 10, 2018 10:56AM
UPDATE 2: Nathan got a quote from another HVAC guy. This one observed that there is a powerful furnace in the basement, set up for hot water, so instead of replacing it with two hot-air furnaces, Nathan could convert the basement furnace with a hot-water-to-air blower, and duct it upstairs. He could also install a second hot-water-to-air blower in the attic, for the attic and second-floor heat, obviating the need for a second hot-air furnace.

Has anyone here had experience with this type of system? Can you comment on the pros and cons? Apparently the cost would be about the same as the two-new-furnaces system.

/Mr Lynn
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Re: HVAC Question—Baseboard Hot Water, or Ducted Hot Air?
Posted by: Winston
Date: January 10, 2018 12:09PM
No experience with that kind of setup, but it strikes me that since most people have hot water heaters, if hot water to air was the most efficient system, that's what people would use. (But then there are hot water baseboard heating systems.)

I don't know if the HVAC guy can do an efficiency comparison between the hot water-based system and new furnaces.

It makes sense that the a standard (gas?) furnace and the hot water system would cost about the same. There's not a whole lot of difference in what needs to be installed. A traditional furnace would need a gas pipe run to it, but running a hot water pipe will cost about the same. Both need a heat exchanger, and controls to turn it on and off. However, the hot water heat exchanger would not need a flue - it would be more like the chiller unit on a system with A/C. (Although see my note above about asking about high efficiency condensing furnaces - they don't need a traditional metal flue, and the flue can run horizontally.)

I doubt you can get the same amount of heat out of a similarly sized hot water to air system as you could from a gas furnace. The burning gas will be a lot hotter than the hot water. So the hot water heat exchanger would have to be larger than a gas furnace heat exchanger would be. Guessing the need for a larger heat exchanger in hot water system makes up for the extra cost of needing a more complex heat exchanger and venting with a traditional gas furnace.

If you go away for the weekend and, say, turn the heat down to 65 (or lower) it will might take longer for the hot water system to warm the house back up. A gas furnace can put a lot of heat out quickly, but it also depends on how the system is sized. In a cold climate you'd need a gas furnace with a pretty good output.


Good luck.

- Winston



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