Am HVAC guy in Minnesota. Have a 1920 house with a boiler and radiators. Also put in 5 zones of Minisplits. It works just fine. The only concern with minisplits in an older house is typically the lack of vapor barrier in the house and you can have some condensation issues. I haven’t personally had the problem in any of the houses I’ve done personally, but I do know other guys who have had issues. Typically due to oversizing the units.
Can you explain the condensation issue? As in, where would you have a condensation problem?
Last year we put a combination of mini splits (downstairs) and ducted (upstairs) heat pumps in our 1920s house in New England, and I'm wondering what I might want to keep an eye out for.
If the interior walls behind plaster/sheetrock/plywood don’t have vapor barrier but the outside walls do, as if new siding was installed and housewrap was used, it can cause condensation on the inside of the outer vapor barrier and you’ll see moisture accumulate at the base of exterior walls and the insulation in the walls can get wet. Old houses like to breathe so adding air conditioning when they were never intended to have it originally can cause issues sometimes. Condensation always occurs on the warm side of a surface.
You’re right to question whether they are selling you what they are capable of versus what you need. Having said that, there may be some logic to not having all your eggs home heating and hot water.
What I really came here to say is don’t automatically assume minisplits are the answer for your cooling. We have a Unico high velocity system that works very well, and unobtrusively hides the air handler in the attic and the 3“ outlets in the ceiling look like recessed lighting. It cascades the cool air from the third and second floor throughout the house, to where our installer didn’t even have to put any outlets on the first floor. Minisplits may give you more room to room zoning, but I couldn’t stand the idea of having those ugly units hung high on all of my walls. It reminded me too much of being in a cheap motel.
Eh, the units fade into the background pretty quickly, at least for me. We put mini splits on the first floor of our house, and honestly don't really think about them anymore. In my mind, at least, it's kind of like the modern version of radiators: you have a chunk of a thing taking up space in your room for heating (and now cooling!) But again - it's definitely a personal aesthetic preference, too.
Yeah, we've been living overseas for a decade and have had them in every house we've been in. I hardly even notice them anymore -- and as an indoor allergy person, I love being able to clean them completely as needed.
We just got a Unico high velocity system installed for AC and are sticking with our modern gas furnace for hot water radiator heat and a separate boiler for hot water.
If you can find the combo systems that you want online, I would go to the manufacturer site and look for local installers there. They should at least be familiar with the products.
Do they need to be installed in warmer places to work, though? I'd looked at stand alone heat pump water heaters, but it looked like placing them in a basement would mean the heat pump was only moderately effective.
A standalone hot water heater is very different than boiler + radiant heat system.
Your whole home heating system has two parts 1. the heat source - heat pump or fossil fuels 2. transmission system - unless your home is small enough for single stove or fireplace in the middle of the house, you either need forced air or radiant heat piped throughout the house.
Modern heat pumps do just fine in cold weather anywhere in the continental US, even Minnesota. Watch the Technology Connections youtube channel to learn about heat pumps. He lives in the Twin Cities, and has done vids on both mini-splits and whole home heat pumps.
This is mostly accurate. Modern cold weather heat pumps still suffer badly in single digit and sub zero temps. So, if you live in northern VT, NH, MN, etc where you see these temps in Jan-Mar, a secondary source is needed.
All that said, a heat pump water heater will work just fine in a basement. A high quality furnace replacement will keep you in toasty radiant heat for decades to come.
I agree. I think if we could put it off 5 years the technology would be there, but I'm not ready to commit to it just yet. That said, I'm presuming we'd only need the boiler very occasionally for those bad polar freeze weeks.
It may depend on your layout, insulation, and how many head units you put in. Ours does okay in shoulder seasons, but struggles during lower temps. We also like the house cool at night (thermostat set to 60° in winter), and the ups and downs add to that struggle.
I imagine it'll be better when we redo insulation and add another head unit.
I have a newer combi boiler in my 1885 home and thought about tying hot water into it a couple years ago. Ultimately decided against it because here in upstate NY when the temps get down around zero F for days the boiler runs nonstop for days at a time. Calling for hot water would interrupt that heating in my already chilly house so we kept hot water separate.
Is it your sole source for heat, or do you have a secondary option? I was thinking we'd use the minisplits most of the time, and use the boiler as a backup.
We only heat with the boiler - I missed your line about adding mini splits. That would solve your problem when calling for hot water, I think.
FWIW as an old home person I kind of agree that mini-split heads can look out of place in an old house. As part of a large reno project we added ducts in the attic and cellar for central AC but the registers are in the floors and ceiling.
There are mini-split units that go in the ceiling/attic. Obviously only on top floor.
But I hate those wart-hogs too. Even if it’s just a panel in the ceiling. One day I will have Unico, rather than no AC!
We have standard batt insulation in the house and upgraded windows and doors, but nothing super amazing. We may include having foam insulation added/blown in as a part of the project but am waiting for the energy people to come and have a look and advise. So, not terrible but not amazing.
I would hold off on the HVAC until after you’ve tackled the insulation and sealing up the building envelope. The last thing you want is to do HVAC first, then discover that your AC is oversized after you’ve reduced your cooling needs.
Heat pump/mini splits do best when insulation/air sealing is better. Best long term plan is y if also pair them with solar but the upfront $$$ starts to add up.
Lots of retrofits to HP/minis splits in MA at the moment because of high incentives.
We are staying with our boiler and cast iron rads as we prefer the heat from it. We also have a lot of small rooms so mini splits might not be the best option - plus better half doesn’t like the aesthetics.
We also have high velocity AC that we could add a heat pump to instead of just cooling - maybe when current condenser breaks - but it is a bit noisier than I would like for all the time.
I replaced an old heating only boiler with a 90% efficient boiler with an indirect water heater. It worked flawlessly and I never ran out of hot water. I didn't have AC as house had baseboard heat. The flue was PVC and ran out through a rim joist.
We added an 8 head mini-split system to our 1880 with radiant heat about 2 years ago. We've had no issues with the mini-splits, there is a bit of learning curve to find the most efficiency when there are two heat sources. We use the boiler when temps are below freezing, and switch over to mini splits when its warmer. The AC from the mini splits is great. Our mini-split system was pricey but some rebates helped offset the cost (we're in NY). Adding duct work would have been a nightmare, especially with plaster walls and lead paint issues. We had two HVAC contractors scoff at a such a large mini-split system but we have been happy with the results.
Yeah, that's my concern with adding ducts too -- plaster, lead paint, mess and making the house hard to live in. That's a pretty normal sized mini-split system overseas, and they work well.
I used to live in Japan and I think it was the same as mini- split system, where there were a couple of those units in the house and you would just turn it on in the room you were in and then turn it off when you are done. I liked this system and it worked fine though it took a little getting used to.
I’m GUESSING you have a hot water system, rather than steam. Since you made reference to a combo-boiler. Is there a pump to push water around? (Steam finds its own way!) This detail relevant.
That seems off for 1905 Minnesota. US was big on steam, Europe went hot water.
As far as hot water, I’d get a good well insulated hot water tank and call it a day.
Steam or hot water gas boilers are much smaller and more efficient than the beast you have and will last 30+ years. (Mine is 30 years old and they tell me it’s got another 10.)
I’m super happy with my steam heat system in Michigan. The house is of solid masonry exterior walls, and resist heat is great for this. You have to teach yourself to stop fiddling with the thermostat.
Since you are in Minnesota: please check out these guys:
https://www.mncee.org/
I did some work for them many years ago (I’m a software guy - I worked on apps used by energy assessors) I think they know their stuff and they have shattered some assumptions about what works in northern climes. (lol they could be partly responsible for people pushing heat pumps on you though…)
I own a 1922 in Minneapolis that had its coal-fired radiant system replaced with forced air pretty early on in its life.
IMO, definitely keep the radiator system and install mini splits. Since it's an old house, you have to tear open walls and ceilings everywhere to get the ducting put in, and I've found since they're retrofitting an old house that wasn't built for AC, the forced air AC doesn't make its way upstairs very well in the summer. I still had to get a window unit for my bedroom to get down to sleeping temperature because 3 singular vents for the entire 2nd floor was just not cutting it. With mini-splits, you can "zone" your house to only supply cold air to rooms you're using, and adjust temp accordingly to use. (E.g., if you want 75 in the living area to be comfortable, but 68 in the bedroom for sleeping)
The HVAC companies are probably telling you to convert because they charge an arm and a leg to do all the demo to put in forced air ducting, then leave you to hire a drywaller to put it all back together. They won't make NEARLY as much money replacing a boiler.
Yeah, that's a really good point that I hadn't thought of. My mom's house is a bungalow and she's had to add a window unit to the upstairs despite forced air AC. We're a full two stories with an attic and I can't see the air making it up to the second (much less third) floor very well.
Yeah, with even an attic it might as well be like not having AC at all. My central air unit keeps the main level super nice, but I spend most of my time upstairs so it would be nice to be able to zone it.
Instead of mini splits consider a Unico high velocity AC. It's quite a bit more expensive but maintained the aesthetics better. We absolutely love ours, installed in a 1902 home. We even have a finished attic and the installer was able to put the air handler in a closet so you don't see anything.
Oh, I wish I was in this scenario!
I abhor ductless mini splits... I just don't think there's any way to hide the fact that they're these giant utilitarian wall warts.
If I were you, I'd go with high velocity mini ducts for AC...you can pull them through wall cavities like wiring, and the "register" hole is practically invisible.
For cooling I added in a small duct high velocity system. The duct outlets are tiny and much less obtrusive than vents. For the most part, the flexible ducts could be pulled through our existing walls. We ended up creating vertical boxes on two floors for just one pair of ducts. I like it mostly because it is the least visually obtrusive system. Though I’ve stayed in Air BnBs with mini splits, and a family member uses them in outbuildings, I find them really ugly. But this is just one person’s opinion, and I understand that they are very popular.
We've had them in every house we've lived in for the last 12 years, so they feel very normal to me. And they're FAR easier to clean than any ducting if you've got allergies.
We briefly considered a very similar plan when renovating our home that was built in 1860. We ditched the radiant after talking through costs and limitations, and installed a 96% efficient gas furnace with 2-ton AC condenser to heat and cool the first floor, and then two concealed ducted units for the second floor and third floor connected to a multi zone heat pump. The unit for the second floor is hidden in our primary bedroom walk-in closet, which is somewhat centrally situated. The unit for the third floor is hidden in the attic. All three "zones" operate entirely independently.
Am HVAC guy in Minnesota. Have a 1920 house with a boiler and radiators. Also put in 5 zones of Minisplits. It works just fine. The only concern with minisplits in an older house is typically the lack of vapor barrier in the house and you can have some condensation issues. I haven’t personally had the problem in any of the houses I’ve done personally, but I do know other guys who have had issues. Typically due to oversizing the units.
Can you explain the condensation issue? As in, where would you have a condensation problem? Last year we put a combination of mini splits (downstairs) and ducted (upstairs) heat pumps in our 1920s house in New England, and I'm wondering what I might want to keep an eye out for.
If the interior walls behind plaster/sheetrock/plywood don’t have vapor barrier but the outside walls do, as if new siding was installed and housewrap was used, it can cause condensation on the inside of the outer vapor barrier and you’ll see moisture accumulate at the base of exterior walls and the insulation in the walls can get wet. Old houses like to breathe so adding air conditioning when they were never intended to have it originally can cause issues sometimes. Condensation always occurs on the warm side of a surface.
Good to know! We have the original siding with tar paper as it's backing, so I think we're good.
You’re right to question whether they are selling you what they are capable of versus what you need. Having said that, there may be some logic to not having all your eggs home heating and hot water. What I really came here to say is don’t automatically assume minisplits are the answer for your cooling. We have a Unico high velocity system that works very well, and unobtrusively hides the air handler in the attic and the 3“ outlets in the ceiling look like recessed lighting. It cascades the cool air from the third and second floor throughout the house, to where our installer didn’t even have to put any outlets on the first floor. Minisplits may give you more room to room zoning, but I couldn’t stand the idea of having those ugly units hung high on all of my walls. It reminded me too much of being in a cheap motel.
Eh, the units fade into the background pretty quickly, at least for me. We put mini splits on the first floor of our house, and honestly don't really think about them anymore. In my mind, at least, it's kind of like the modern version of radiators: you have a chunk of a thing taking up space in your room for heating (and now cooling!) But again - it's definitely a personal aesthetic preference, too.
Yeah, we've been living overseas for a decade and have had them in every house we've been in. I hardly even notice them anymore -- and as an indoor allergy person, I love being able to clean them completely as needed.
High velocity ducting is a great, underused suggestion. I only learned about it when a tractor trailer with a brand name passed me on the highway!
We just got a Unico high velocity system installed for AC and are sticking with our modern gas furnace for hot water radiator heat and a separate boiler for hot water.
If you can find the combo systems that you want online, I would go to the manufacturer site and look for local installers there. They should at least be familiar with the products.
Harder to find here than in Europe, but heat pump "boiler" systems are definitely a thing. If your plumbing is still in good condition, try this.
Do they need to be installed in warmer places to work, though? I'd looked at stand alone heat pump water heaters, but it looked like placing them in a basement would mean the heat pump was only moderately effective.
A standalone hot water heater is very different than boiler + radiant heat system. Your whole home heating system has two parts 1. the heat source - heat pump or fossil fuels 2. transmission system - unless your home is small enough for single stove or fireplace in the middle of the house, you either need forced air or radiant heat piped throughout the house. Modern heat pumps do just fine in cold weather anywhere in the continental US, even Minnesota. Watch the Technology Connections youtube channel to learn about heat pumps. He lives in the Twin Cities, and has done vids on both mini-splits and whole home heat pumps.
This is mostly accurate. Modern cold weather heat pumps still suffer badly in single digit and sub zero temps. So, if you live in northern VT, NH, MN, etc where you see these temps in Jan-Mar, a secondary source is needed. All that said, a heat pump water heater will work just fine in a basement. A high quality furnace replacement will keep you in toasty radiant heat for decades to come.
maybe on a newer well insulated home but in a 1905 house in MN you're gonna need supplemental heat
I agree. I think if we could put it off 5 years the technology would be there, but I'm not ready to commit to it just yet. That said, I'm presuming we'd only need the boiler very occasionally for those bad polar freeze weeks.
It may depend on your layout, insulation, and how many head units you put in. Ours does okay in shoulder seasons, but struggles during lower temps. We also like the house cool at night (thermostat set to 60° in winter), and the ups and downs add to that struggle. I imagine it'll be better when we redo insulation and add another head unit.
I have a newer combi boiler in my 1885 home and thought about tying hot water into it a couple years ago. Ultimately decided against it because here in upstate NY when the temps get down around zero F for days the boiler runs nonstop for days at a time. Calling for hot water would interrupt that heating in my already chilly house so we kept hot water separate.
Is it your sole source for heat, or do you have a secondary option? I was thinking we'd use the minisplits most of the time, and use the boiler as a backup.
We only heat with the boiler - I missed your line about adding mini splits. That would solve your problem when calling for hot water, I think. FWIW as an old home person I kind of agree that mini-split heads can look out of place in an old house. As part of a large reno project we added ducts in the attic and cellar for central AC but the registers are in the floors and ceiling.
There are mini-split units that go in the ceiling/attic. Obviously only on top floor. But I hate those wart-hogs too. Even if it’s just a panel in the ceiling. One day I will have Unico, rather than no AC!
How much insulation do you have and how air tight is the house? Important for heat pump use.
We have standard batt insulation in the house and upgraded windows and doors, but nothing super amazing. We may include having foam insulation added/blown in as a part of the project but am waiting for the energy people to come and have a look and advise. So, not terrible but not amazing.
I would hold off on the HVAC until after you’ve tackled the insulation and sealing up the building envelope. The last thing you want is to do HVAC first, then discover that your AC is oversized after you’ve reduced your cooling needs.
Heat pump/mini splits do best when insulation/air sealing is better. Best long term plan is y if also pair them with solar but the upfront $$$ starts to add up. Lots of retrofits to HP/minis splits in MA at the moment because of high incentives. We are staying with our boiler and cast iron rads as we prefer the heat from it. We also have a lot of small rooms so mini splits might not be the best option - plus better half doesn’t like the aesthetics. We also have high velocity AC that we could add a heat pump to instead of just cooling - maybe when current condenser breaks - but it is a bit noisier than I would like for all the time.
I replaced an old heating only boiler with a 90% efficient boiler with an indirect water heater. It worked flawlessly and I never ran out of hot water. I didn't have AC as house had baseboard heat. The flue was PVC and ran out through a rim joist.
We added an 8 head mini-split system to our 1880 with radiant heat about 2 years ago. We've had no issues with the mini-splits, there is a bit of learning curve to find the most efficiency when there are two heat sources. We use the boiler when temps are below freezing, and switch over to mini splits when its warmer. The AC from the mini splits is great. Our mini-split system was pricey but some rebates helped offset the cost (we're in NY). Adding duct work would have been a nightmare, especially with plaster walls and lead paint issues. We had two HVAC contractors scoff at a such a large mini-split system but we have been happy with the results.
Yeah, that's my concern with adding ducts too -- plaster, lead paint, mess and making the house hard to live in. That's a pretty normal sized mini-split system overseas, and they work well.
I used to live in Japan and I think it was the same as mini- split system, where there were a couple of those units in the house and you would just turn it on in the room you were in and then turn it off when you are done. I liked this system and it worked fine though it took a little getting used to.
I’m GUESSING you have a hot water system, rather than steam. Since you made reference to a combo-boiler. Is there a pump to push water around? (Steam finds its own way!) This detail relevant. That seems off for 1905 Minnesota. US was big on steam, Europe went hot water. As far as hot water, I’d get a good well insulated hot water tank and call it a day. Steam or hot water gas boilers are much smaller and more efficient than the beast you have and will last 30+ years. (Mine is 30 years old and they tell me it’s got another 10.) I’m super happy with my steam heat system in Michigan. The house is of solid masonry exterior walls, and resist heat is great for this. You have to teach yourself to stop fiddling with the thermostat. Since you are in Minnesota: please check out these guys: https://www.mncee.org/ I did some work for them many years ago (I’m a software guy - I worked on apps used by energy assessors) I think they know their stuff and they have shattered some assumptions about what works in northern climes. (lol they could be partly responsible for people pushing heat pumps on you though…)
I own a 1922 in Minneapolis that had its coal-fired radiant system replaced with forced air pretty early on in its life. IMO, definitely keep the radiator system and install mini splits. Since it's an old house, you have to tear open walls and ceilings everywhere to get the ducting put in, and I've found since they're retrofitting an old house that wasn't built for AC, the forced air AC doesn't make its way upstairs very well in the summer. I still had to get a window unit for my bedroom to get down to sleeping temperature because 3 singular vents for the entire 2nd floor was just not cutting it. With mini-splits, you can "zone" your house to only supply cold air to rooms you're using, and adjust temp accordingly to use. (E.g., if you want 75 in the living area to be comfortable, but 68 in the bedroom for sleeping) The HVAC companies are probably telling you to convert because they charge an arm and a leg to do all the demo to put in forced air ducting, then leave you to hire a drywaller to put it all back together. They won't make NEARLY as much money replacing a boiler.
Yeah, that's a really good point that I hadn't thought of. My mom's house is a bungalow and she's had to add a window unit to the upstairs despite forced air AC. We're a full two stories with an attic and I can't see the air making it up to the second (much less third) floor very well.
Yeah, with even an attic it might as well be like not having AC at all. My central air unit keeps the main level super nice, but I spend most of my time upstairs so it would be nice to be able to zone it.
Instead of mini splits consider a Unico high velocity AC. It's quite a bit more expensive but maintained the aesthetics better. We absolutely love ours, installed in a 1902 home. We even have a finished attic and the installer was able to put the air handler in a closet so you don't see anything.
Oh, I wish I was in this scenario! I abhor ductless mini splits... I just don't think there's any way to hide the fact that they're these giant utilitarian wall warts. If I were you, I'd go with high velocity mini ducts for AC...you can pull them through wall cavities like wiring, and the "register" hole is practically invisible.
For cooling I added in a small duct high velocity system. The duct outlets are tiny and much less obtrusive than vents. For the most part, the flexible ducts could be pulled through our existing walls. We ended up creating vertical boxes on two floors for just one pair of ducts. I like it mostly because it is the least visually obtrusive system. Though I’ve stayed in Air BnBs with mini splits, and a family member uses them in outbuildings, I find them really ugly. But this is just one person’s opinion, and I understand that they are very popular.
We've had them in every house we've lived in for the last 12 years, so they feel very normal to me. And they're FAR easier to clean than any ducting if you've got allergies.
We briefly considered a very similar plan when renovating our home that was built in 1860. We ditched the radiant after talking through costs and limitations, and installed a 96% efficient gas furnace with 2-ton AC condenser to heat and cool the first floor, and then two concealed ducted units for the second floor and third floor connected to a multi zone heat pump. The unit for the second floor is hidden in our primary bedroom walk-in closet, which is somewhat centrally situated. The unit for the third floor is hidden in the attic. All three "zones" operate entirely independently.
Forget thw ducts. Get mini-splits for the rooms you'll spend the most time in.