Figuring out HVAC approach for our home

[illini81]

Ok here’s the long story. My wife and I bought at 2400 sqft colonial in Eastern CT a year ago. It has a 1000 sqft finished basement, so 3400 sqft overall. Every house has it’s pros and cons. The cons of this house were a neglected exterior (which we’re tacking ourselves), and a bad HVAC combo – window units for AC and electric baseboard heat.

Before buying the house, we asked for a year of utility bills from the prior owner. It almost caused us to walk away. Their annual utility bills (propane for hot water heat and fireplace, and electric) totaled $5500. And that was with a mild winter that year!

We ended up deciding to put in a wood stove to bring down heating costs, and that has worked nicely so far this year. The stove (on our main level) can heat the whole house easily until daytime temps get down to about 25 degrees. With increasing difficulty (i.e. need 3 full loads instead of two a day), it can heat the whole house down to about 15 degrees. After that, it can’t keep up. At the moment we are using baseboard heat in our daughters’ rooms, since we close their doors for noise. Comparing our utility bills to the prior owners’ bills, we have saved $2700 heating with wood.

However, when we eventually sell the house (no plans to do so in the near future), I am afraid that our HVAC combo will be unattractive to buyers. In the price range that our home is in, probably about half of the local homes have central air. We are planning on doing some relatively significant remodeling (taking down some walls to open up the main level). I think this, along with other features of our house (very desirable location, great lot, etc) could add quite a bit to the value of our home. However, as you get into price ranges above what we paid for our home, more and more houses have central air. Also, my perception is that many people don’t think of a wood stove as a plus. We knew this when we bought it, and decided it would pay for itself.

So here are the options we’re exploring, that I’d love to get experienced input on:

1. Install central air for heating and cooling – we would still use our stove to provide the majority of our heating needs. The central air would kick in when it gets really cold, and it’s possible that we’d use it for the shoulder season. Since we don’t really need the central air, I would consider looking for a relatively cheap system. The main purpose of the system would be to add resale value to the home. The system would use oil (don’t have access to natural gas).
   
   
2. Install a heat pump. I had never heard of heat pumps until joining hearth.com. It seems that there are many people on here who have them. It makes sense to me that they pair well with wood stoves, since they’re most efficient in shoulder season temps. My perception was that this would be a cheaper option than installing central air. However, I got a quote this week for $30k () for a 5 head system (two downstairs, 3 upstairs for bedrooms). The contractor told me he sells heat pumps that are “good down to -15 degrees”. I’m not sure exactly what that means (I thought heat pumps are relatively inefficient as temperatures get colder?). I’m going to try to get another quote next week. Do I need to make it clear that I am only looking for a system to heat when it’s above 40ish degrees? I’m assuming that would bring down the price dramatically?

I’ve tried to find good info on heat pumps, since I know nothing about them. Mostly I’ve found promotional material though, or really basic explanations of how they work. I’d appreciate any advice/help from fellow hearth.com members. This is a pretty sharp community, and I’m guessing there are some people on here who know quite a bit about heat pumps. Sorry for the really long post…

 

[JimBear]

There is a thread on here somewhere about heat pumps & the differences between them. I can’t remember which forum it was in. Maybe do a search.

 

[moey]

Heck for 30k you can probably get a geothermal system that will work for all temperatures. Theres a 30% tax break.

You probably would not save much going with heat pumps that only go down to 40ish. Your paying for labor for the most part and getting gouged although I know in CT things are more expensive.

If your doing major renovation work consider putting in central heating system that is not electric oil, propane, geothermal system. I think putting mini splits all over the place like your 30K quote probably is not the best idea.

 

[blades]

best bet is central heat and cool although you might need two units as it sounds like you have a second floor. Only because it would be much simpler to duct a separate unit from the attic for the second floor rather than trying to be creative in running duct work up through walls ( can of worms) 1k sq ft per unit about a 65btu furnace for each floor I would stay with the propane for these as the tank is already there, and they are a bit cheaper than a oil burner. Additionally in the 90 plus range efficiency wise they can be vented with pvc. Cost heat wise not lot of difference with perhaps a slight edge to the LPG. AC can set up in the traditional manor ( A coil above plenum or a horizontal system for the upstairs if locating it in attic) with these as well. So that would possible be 2 condensers also. Key to any of this is to maximize insulation and minimize air leakage. Just some ideas off the top.

 

[DickRussell]

You are making a mistake by looking for a cheap way to throw heat into a house that squanders it through construction that is either shoddy or done at a time when energy costs were not such a big deal as today. With a house like this, always put your first money into heat conservation, and that begins with a thorough energy audit by someone who knows what he is doing. Part of this will include a blower door test to measure leakiness and locate the big leaks. Blower door-directed air sealing will pay off handsomely. This is the "low hanging fruit" that pays the most for the cost invested. The investigator will be able to recommend further measures to improve insulation levels.

 

[peakbagger]

A few questions. Have you had a energy audit done to the house?. The cheapest way to heat is not having to heat as often by tightening up the house to being with. Most New England states have subsidized energy audits through the local utility.

Do you have ductwork in the house?. Does it run inside the heated space? If its undersized, leaky or runs through unheated spaces it may mean it not worth using it and limits your options for HVAC.

There are three basic heat pump concepts. They all use the same basic guts but in different ways. They are electric heating devices but because of how they work, they use less power than resistance heat. There really is no oil option for a standard heat pump, it needs electricity to run it. Heat pumps just move heat around instead of creating it. In the summer they "pump" heat out of the house to the outdoors and in the winter they pump heat from the outdoors to the indoors. They use a refrigerant to move the heat around and its density changes depending on the temperature. The actual piece of equipment that does the work is the compressor. The compressor can run at fixed speed or variable speed. Fixed speed compressors don't deal well with below freezing temperatures and usually only work down to about 40 degrees, anything less than that and they have electric heaters built into them to supply heat at lower temps. Variable speed units can run at lower temps. Due to the physics of how they work, heat pumps are much better at putting out a lot of warm air instead of hot air.

The three types are; whole house heat pumps, mini splits and then a specialized type of whole house heat pump called a geothermal heat pump. A whole house heat pump is typically tied to duct work. The duct work moves air around the building and back to the air handler where there are coils from the heat pump that either heat the air or cool the air in the ducts. The "devil" with a whole house heat pump is there is lot of potential for heat or cooling to leak out the duct into unconditioned spaces via air leaks or poor insulation. It also requires a big fan to move the air around. Whole house units typically switch over to regular resistance heat below 40 degrees due to issues with ice forming on the outdoor coils.

Mini Splits are newer to the market. They don't use duct work to move the heating or cooling around. There is an outdoor unit that is directly connected to an indoor air handler via bundle of tubing (about 4" in diameter) in each room to be conditioned. In some cases, you can have one outdoor unit service three air handlers. These units can also be built for much colder weather operation, some down to -10 degrees F although down at the very low temps, they put out less heat and the efficiency goes down to the point where its approaching electric resistant heat. These cold weather units cost more than a standard unit that only works down to 40 degrees. They are quite popular for retrofitting homes that want cooling and heating. The trade off is if you have a lot of small rooms with poor air flow, you need a lot of air handlers in each room. Unless you need precise temperature control you can normally put in few units in the major rooms and put up with a bit of temperature variation. I heat and cool one and half floors in my small house with one unit and its the only thing I use when the temps go over 30 F.

A geothermal heat pump is special variation of a whole house unit. Instead of pumping heat from outdoor air it pumps heat from the ground which is typically steady temperature once you get several feet down. They can either exchange heat through drilled wells or through direct buried loops. If designed correctly, they are more efficient in winter and summer as the ground temps are lot more steady than the outdoors temps. The indoor part of the system looks like a standard heat pump and usually ties into ductwork. They tend to require larger ductwork through the house as they tend to put out lower temps. The trade off with these systems is the cost to build them is steep. I someone goes the drilled well route, they may need several drilled well holes, if they go with direct burial, the size of the area to be excavated will be several times larger than the house foundation. They require the least energy input if designed correctly but generally they are used in high end homes where the premium for the installation is a smaller percentage of the overall home cost. They are also popular in government uses as there are sometime big subsidies for being "green". Generally the house is designed around geothermal heat pumps, they can be retrofit but its even more expensive.

Hard to make generalizations. The no brainer is have an energy audit done and tighten up the house. From there if you want heating and cooling go with minisplits with the cold weather option using a wood stove to supplement the winter heating load. The key with minisplits is the outdoor unit placement is critical. They need to be elevated off the ground high enough to avoid snow and situated so that snow doesn't blow into the coils. There are special baffles that can be installed but the important part is to install them right to begin with. The nice thing is you don't need to do the entire house at once. Install a unit in the most important room(s) and see how it works.

I realize CT has high electric power costs so a very good match is net metered solar. There are very good incentives in some parts of CT for solar so if you have the site for it consider it to offset the power use.

 

[illini81]

Thanks all for the replies. This is awesome.

I actually did have an energy audit done (should have mentioned this right off the bat). The audit was actually what started me down the road of thinking about either central air or a heat pump system – they are offering rebates on both right now. The blower air test confirmed what we had already found out about our house – that it is pretty tight. I forget the units, but the target leakage for a house of our size/layout is 24000, and the tested leakage was 2000. The contractors said that if we tightened it up any more, we might have issues with the air in the house not being replaced often enough.

In addition to having a tight house, we have a very shaded house (80-100 ft tall oaks on all four sides). Because of the shade, insulation and our climate, we only “need” AC for a few months out of the year. We were actually too lazy to even install our window units last summer, although it was a pretty mild summer.

The main reasons I’d want to get either central air or a heat pump system are 1. Resale value (see my explanation above) and heating in the shoulder season.

 

[illini81]

A few questions. Have you had a energy audit done to the house?. The cheapest way to heat is not having to heat as often by tightening up the house to being with. Most New England states have subsidized energy audits through the local utility.

Do you have ductwork in the house?. Does it run inside the heated space? If its undersized, leaky or runs through unheated spaces it may mean it not worth using it and limits your options for HVAC.

There are three basic heat pump concepts. They all use the same basic guts but in different ways. They are electric heating devices but because of how they work, they use less power than resistance heat. There really is no oil option for a standard heat pump, it needs electricity to run it. Heat pumps just move heat around instead of creating it. In the summer they "pump" heat out of the house to the outdoors and in the winter they pump heat from the outdoors to the indoors. They use a refrigerant to move the heat around and its density changes depending on the temperature. The actual piece of equipment that does the work is the compressor. The compressor can run at fixed speed or variable speed. Fixed speed compressors don't deal well with below freezing temperatures and usually only work down to about 40 degrees, anything less than that and they have electric heaters built into them to supply heat at lower temps. Variable speed units can run at lower temps. Due to the physics of how they work, heat pumps are much better at putting out a lot of warm air instead of hot air.

The three types are; whole house heat pumps, mini splits and then a specialized type of whole house heat pump called a geothermal heat pump. A whole house heat pump is typically tied to duct work. The duct work moves air around the building and back to the air handler where there are coils from the heat pump that either heat the air or cool the air in the ducts. The "devil" with a whole house heat pump is there is lot of potential for heat or cooling to leak out the duct into unconditioned spaces via air leaks or poor insulation. It also requires a big fan to move the air around. Whole house units typically switch over to regular resistance heat below 40 degrees due to issues with ice forming on the outdoor coils.

Mini Splits are newer to the market. They don't use duct work to move the heating or cooling around. There is an outdoor unit that is directly connected to an indoor air handler via bundle of tubing (about 4" in diameter) in each room to be conditioned. In some cases, you can have one outdoor unit service three air handlers. These units can also be built for much colder weather operation, some down to -10 degrees F although down at the very low temps, they put out less heat and the efficiency goes down to the point where its approaching electric resistant heat. These cold weather units cost more than a standard unit that only works down to 40 degrees. They are quite popular for retrofitting homes that want cooling and heating. The trade off is if you have a lot of small rooms with poor air flow, you need a lot of air handlers in each room. Unless you need precise temperature control you can normally put in few units in the major rooms and put up with a bit of temperature variation. I heat and cool one and half floors in my small house with one unit and its the only thing I use when the temps go over 30 F.

A geothermal heat pump is special variation of a whole house unit. Instead of pumping heat from outdoor air it pumps heat from the ground which is typically steady temperature once you get several feet down. They can either exchange heat through drilled wells or through direct buried loops. If designed correctly, they are more efficient in winter and summer as the ground temps are lot more steady than the outdoors temps. The indoor part of the system looks like a standard heat pump and usually ties into ductwork. They tend to require larger ductwork through the house as they tend to put out lower temps. The trade off with these systems is the cost to build them is steep. I someone goes the drilled well route, they may need several drilled well holes, if they go with direct burial, the size of the area to be excavated will be several times larger than the house foundation. They require the least energy input if designed correctly but generally they are used in high end homes where the premium for the installation is a smaller percentage of the overall home cost. They are also popular in government uses as there are sometime big subsidies for being "green". Generally the house is designed around geothermal heat pumps, they can be retrofit but its even more expensive.

Hard to make generalizations. The no brainer is have an energy audit done and tighten up the house. From there if you want heating and cooling go with minisplits with the cold weather option using a wood stove to supplement the winter heating load. The key with minisplits is the outdoor unit placement is critical. They need to be elevated off the ground high enough to avoid snow and situated so that snow doesn't blow into the coils. There are special baffles that can be installed but the important part is to install them right to begin with. The nice thing is you don't need to do the entire house at once. Install a unit in the most important room(s) and see how it works.

I realize CT has high electric power costs so a very good match is net metered solar. There are very good incentives in some parts of CT for solar so if you have the site for it consider it to offset the power use.

Thanks for the very detailed reply. This really helped me to understand several of the things that confused me about heat pumps/mini splits. This is a much better explanation than any I have found elsewhere. I do not have any ductwork currently.

 

[illini81]

A floorplan of the main level of our house is attached.

We spend most of our time in the family room/sunroom/playroom. The stove is able to heat the whole house by heating that room, without unacceptable temperature variation throughout the house. That room stays 68-74, the LR and study are usually 65-70, and upstairs is 62-67.

Would it be reasonable to assume that a well sized minisplit in the family room would similarly be able to heat the whole house during the shoulder season? For example, when we have 40 degree nights and 50 degree days, do you think a minisplit in that location could keep the downstairs around 70 and the upstairs in the low 60’s?

From what the salesman said, it is the heads that add up. He said it would be about $5k per head inside the house. So that makes me wonder – would it make sense to mix central air and minisplits? Having four bedrooms upstairs would require a bunch of heads. However, I could put in one or two minisplits on the main level and then central air to take care of the upstairs bedrooms. This would have the following advantages:

1. Would provide the energy saving advantages of “zoning”. During the day when we’re mostly just downstairs, the heat pump would be running to heat/cool the space we were in (unless it was stove weather). During the night, when we’re upstairs, we’d turn off the heat pump and run the central air. Unless we were heating, and it was mild enough weather that the heat pump could heat the whole house.

2. Would benefit from the efficiency of a heat pump without having to pay for a ton of heads that seem to drive up the cost

3. From the little I’ve read, it sounds like the labor associated with running ducts is what causes central air to be expensive. I would think that solely running ducts in the attic would be fairly cheap, since the ducts aren't running in closets/behind walls, etc.

Is this just too complicated?

 

[blades]

insulated ducts round or rectangular are available from diy stores. Goodman is a primary mfg of heating units and ac units- and supply many other brands. The last Goodman hvac system I installed had about 6 brand name labels in the packaging so you could select what name you wanted. You can purchase units on line at a pretty good savings vs from a dealer and still find an installer. 7 years back replaced hvac system in that home 2000 ft ranch total cost $1800 installed- duct work was already in place. But as I said most of the duct work can be had at diy stores with maybe one or two transition pieces that may need to be made up. Acentral system will go a long way for your anticipated sale as well as the new owners acquiring insurance. Not everyone is on board with the latest and greatest cutting edge equipment and prefer to stay within their particular comfort zone, including insurance companies. Course all of this hi tec stuff relies on electric power some more than others, so having back up heating is a plus ( wood stove), pellet stove,geo thermal, owb,heat pumps require power to operate. Solar and wind power systems can be a can of worms- not trying to rain on peakbagger or some others with large solar arrays - but they are only worth while if there are enough perks from various sources to bring the costs down to a 1 or 2 year breakeven point. In my area there isn't squat for these items or I simply do not qualify ( I have yet to figure that out- no details all political)

 

[peakbagger]

Unless you are planning to condition the attic space, its not recommended to run ducts outside of conditioned spaces.

5K per head sounds steep for a mini split. I would guess 4K for a 1 ton cold climate mini split.

 

[Highbeam]

You do realize that central air and a heat pump are the same thing right? Mini splits also provide heating and cooling using “heat pump” technology but without ducts.

If you really plan on installing ducts for central air then you are pretty much done with your decision making process.

I too have an old house with no ductwork. Adding ducts properly is the hard part.

 

[illini81]

You do realize that central air and a heat pump are the same thing right? Mini splits also provide heating and cooling using “heat pump” technology but without ducts.

If you really plan on installing ducts for central air then you are pretty much done with your decision making process.

I too have an old house with no ductwork. Adding ducts properly is the hard part.

I did realize that... but I only learned that just recently, and so I think I've been using the terms interchangeably. My bad! Sorry to be unclear. When I say heat pump, I mean ductless minisplit.

 

[illini81]

If you really plan on installing ducts for central air then you are pretty much done with your decision making process.

So it sounds like my "half ductless half ducted" idea is a bad one huh. It just seems like conditioning the entire house is going to be prohibitively expensive if I do it solely with ductless minisplits and although I haven't gotten a quote for central air, my guess is that it would be easily in the 20k range as well. Argg.

 

[peakbagger]

There are hybrid systems where there are separate air handlers for different areas of the house where instead of running ducts, refrigerant is pumped around. Part of the problem is the"This Old House Effect", the systems installed are show case systems where equipment manufacturers are paying to have their equipment showcased. Folks see the show and think that what they are seeing is a standard installation. Standard for a half a million plus home but pretty darn expensive to install and maintain for a 250K home. Not many folks hauling around firewood for a 500K plus home.

Back to an energy audit to begin with, reduce the load and the up front cost for equipment is lower and the ongoing costs are also lower. I have a tight home and have cellular blinds with side seals on the windows. The footprint of my main floor is 28 by 34 and consists of 4 rooms. I can cool the entire first floor with a single 12,000 BTU (1 ton) minisplit. If its going to be hot and humid I need to run it for a couple of hours in order to knock the humidity out of the air before the air temps drop but the trade off its a much smaller than a standard central heat pump and usually more efficient when duct loss is taken in account. Once the humidity is knocked down, even on the hottest day the actual cooling part of the unit is not running all the time, its just recirculating the air. The problem is most folks want to air condition a bright sunny room with little or no outdoor shading with sun streaming in through the windows.

Many older homes were designed to optimize solar gain which is nice on a spring day but is major problem when they need to be cooled. They were designed for cheap energy. Unless you plan to improve the building envelope, switching fuels can only save you so much and once you add air conditioning the total cost to heat and cool will increase. The nice part of tightening a house up which usually starts by reducing air infiltration is you save in the winter and summer by not having to heat and cool air being sucked in from the outdoors.

 

[Highbeam]

So it sounds like my "half ductless half ducted" idea is a bad one huh. It just seems like conditioning the entire house is going to be prohibitively expensive if I do it solely with ductless minisplits and although I haven't gotten a quote for central air, my guess is that it would be easily in the 20k range as well. Argg.

Sure, you could install separate heating systems for each room. If you are adding central ducted air I would assume (as would other buyers) that this is done for the entire home. One system or type of system for the whole place is expected. Based on that assumption you'll have ductwork for all space and a very logical, cost effective, traditional, normal, sellable, way to provide heating, cooling, filtration, humidity control, etc. to the home.

Minisplits work great and are cost effective until you need a multihead system. Then efficiency goes down and price goes way up. Plus, subjectively, I think the inside wall units are especially stupid and cheap looking. Their air filtration abilities are relatively poor. Fortunately in the last several years the conventional split systems have picked up most of the technology improvements.

 

[MAD777]

Just to add a data point, last week I priced two systems for new construction. The house will have 2320 sq. ft. of living space in the White Mountains of NH.
One system was a mini-split and the other, propane heat. (Most people do not have A/C in the Whites). Both prices included hot water.
Mini-split = $29,000
Propane = $17,000 incl. 500gal tank
Obvious advantage of the mini-split is having A/C.
The advantage of propane is an infinite supply of on-demand hot water.
I was feeling pretty good about mini-splits until I got the price. Plus, we had a week of negative 20's this year, which shook my confidence.



Sent from my SM-G900V using Tapatalk

 

[shoot-straight]

todays heat pumps are remarkably efficient even at cold temps. very, very efficient in cool temps though. i think a heat pump with natural gas backup is the most efficient choice. it a better choice over electric backup.

 

[peakbagger]

Quite a difference in climate zones and seasonal lows between Eastern CT and the Whites of NH. A quick look at ASHRAE has Eastern CT as having a winter design temp of 15 deg F while Berlin is -10.7 deg F with Laconia around 0. That makes big difference in the suitability of mini split since the performance really degrades based on my observations below 20 degree F with it really tapering off below zero. Its also dependent on the wet bulb temp, cold and dry means fewer defrost cycles while cold and damp, means frequent defrost cycles.

I don't think any responsible contractor would recommend minisplits in the whites of NH as a primary source of heating which calls into question the estimate basis. Looks to me like the contractor wants to install propane . Given the much lower potential winter temps in central to northern NH, minisplits are regarded as supplemental heat to another base heating source. I have talked to folks who have vacation condos in the area that have minisplits but in all cases they have electric baseboard as a fall back. That works and is also nice for weekend use as they can crank up the baseboard to get the place initially warm and then switch to the minisplit for the balance of the weekend in winter.

FYI, some Fujtsu dealers hype that they have "heaters" on their units compared to the competition (Mitsubishi). That's a lot of hype as the heater is a pan heater that keeps the condensation pan from icing up. This heater does not contribute to the system efficiency but does have some advantage for units that are poorly located and subject to snow blowing in them. Knock on wood, my Mitsubishi unit has been running for several years and the only time I have had an ice up is when I accidently aimed my snowblower chute at it and filled the entire case with snow. I am surprised that either company doesn't offer a optional heating coil for the indoor unit but expect it would require a redesign as currently the wiring feed from the outdoors t the indoors is just control wiring and a low amperage fan. Putting in a heater would mean a much larger feeder.

Large central heat pumps work fine at low temps, the owner just needs to understand that they are typically heating with electric resistance heat down below freezing unless they use geothermal.

 

[begreen]

If you are going with a ducted central air system ducting the first floor is pretty straight forward if the basement has adequate headroom and is reasonably open. Heating/Cooling the upstairs may present a bigger challenge due to the difficulty of hiding the supply plenum and take-offs. This depends on the house layout and available run locations like knee wall spaces. In our house because of these limitations I ran two ducts upstairs, on to the large master bedroom and one to the hallway. It's not perfect but does an adequate job in part helped by a large open stairway going upstairs. I ran one 6" duct up a bathroom closet and another flat duct up in a wall with a small soffit to clear the top plate.

Another alternative and potentially more efficient for heating would be to install a hydronic system using a high efficiency oil boiler. That requires much less room real estate for chasing piping to the second floor. A hydronic system opens the option for cooling as well if hydronic air handlers are use. This is how my brother-in-law's house in mid-state NY is heated and cooled. It works well. The thermal capacity of water is impressive. The addition of an air to water heat pump may also be attractive to this setup.
http://www.radiantprofessionalsalliance.org/HIA/Documents/Articles/WWNL-3-15.pdf

 

[fbelec]

typical duct system with a dual fuel air handler. meaning like a york affinity dual fuel it's a two speed heat pump that has a defrost cycle. it will go down to the mid 30's and it can be set to 32. them when it gets down to the 32 mark it switches to the other fuel nat gas or propane not sure if the are doing oil yet i do know that there is a oil forced hot air unit that is 90% eff and uses a pvc pipe for a exhaust no chimney

 

[georgepds]

"Not many folks hauling around firewood for a 500K plus home."

uh oh... if the assessment goes up another 50k I'll have to turn in the Woodstock

More on topic
1 how big is the woodstove.. for a tight house a big stove should heat the whole house. Mine does, just north of you in Massachusetts on 2chords a year, down to -10F. ... or, just put in more wood

2 a mini split downstairs will probably help you a lot... rule of thumb is 12k btu/hr for each 600ft2 of floor. Do a manual J if you want better sizing

 

[begreen]

Yeah, depends on the neighborhood. Lately property values are going up so quickly that the average home is over $500k. There are lots of wood burners in these homes, especially if power outages are common. Actually we get several people a year in the main forum asking about heating their 3-4,000 sq ft homes with wood. I think a lot of them bought McMansions and are now facing high heating bills for all the cubic footage.

 

[maple1]

It is usually a huge PITA to retrofit duct work into a two story house. And I would not want duct work in any unconditioned spaces (i.e, attic). [I don't like it much to start with, takes up a lot of space].That would likely be the determining factor for me, and lead me to a non-central solution. However, if your upcoming extensive remodels will allow it to happen - that might be a tipping point. In which case I would likely go with a new modern efficient central heat pump for heat & A/C.

But, just from what I have read, I am also thinking that if you can keep your place warm enough with your stove, you should be able to keep it warm with a couple of mini-splits.

I am finding those quotes for mini-splits pretty extravagant though. I think a single head unit around here all-installed is in the 4-5000 range. Running another head maybe another 2000. Situation specific, of course. I would not get anything but the most efficient that can heat down in the lower ranges - I don't think the up front minimal cost savings in going to a less efficient one would pay off long term, and would be much less appealing to a future buyer.

Likely no one 'right' answer - but for me it would likely all hinge on whether or not you can get proper duct work economically installed to service the whole house without putting any into unconditioned spaces.

 

[peakbagger]

I agree the mini-split costs seem quite high but I have heard CT has sky high labor costs for contractors. When I look at the tables in RS Means for Electrical labor they show a 33% adder for Norwalk and Stanford labor.

HVAC rules of thumb should be taken with a major grain of salt. There are two types of HVAC loads, latent and sensible. Latent is roughly the amount of moisture in the air that needs to be condensed out of the air. Sensible is the actual air temp. New England in general especially coastal new England tends to have high relative humidity which means there is lot of water vapor in the air. A persons body uses sweat for cooling and if the relative humidity is high it takes a lower room temp to be comfortable. Humidity in the air is sneaky stuff, if there are significant gaps in the envelope between the outdoors and indoors, the humidity will quickly flow to the driest spot to equalize the humidity. When an AC unit is first turned on most folks complain it takes a very long time to get the temperature to drop and that is because the AC unit is spending most of its cooling power to condense water vapor into liquid and hopefully drain it out of the space. That's where the energy audit comes in as a first thing they will do is a blower door test and most likely the test means they are going to concentrate on sealing gaps in the exterior envelope. The other big source of household moisture is a basement. Unless there is a vapor barrier inside or outside the walls and floors, the concrete or stone acts as a wick for soil moisture to flow into the basement and then into the house. That is not dealt with in standard calculations and as such it means the results can be conservative for a modern home built to current energy standards and codes. It pretty universal that folks with Passiv type homes built with tight vapor barriers report that they can heat and cool much larger spaces then typical rules of thumb would expect.

Unfortunately most folks who extensively renovate rarely spend a lot of money energy retrofitting. To do it right its a PITA and since its hidden most folks would much prefer to spend their money elsewhere. I did open up one wall of my place several years ago and did the flash and batt method of reinsulating the 6" wall. I took out the fiberglass insulation and then sprayed about two inches of foam against the exterior wall, then I reinstalled the same fiberglass batts on top of them. I also installed 1/2" of isoboard foam on top of the studs and then sheetrocked over it.

A FYI is most standard bathroom vents are installed poorly, many just vent up above the ceiling into the attic and a lot of that moisture may short circuit back into the house. Ideally the vent needs to be vented outside away from soffits vents preferably where there is air flow to carry the moisture away from the house. I admit my system is not ideal and I have been thinking of long term fix.