Reality of solar heat?

[PNW_Steve]

Hey Everyone,

As Winter sets in my frustration follows...

I live in S.E. Washington State in a 2200sf house that was built in the late 40's to early 50's. It has been remodeled with double pane windows and 1" of EPS foam board wrapped the exterior walls. It also sports a 1.5 ton Goodman heat pump.

My frustration comes from trying to maintain 67F in the downstairs of the house. We keep the upstairs bedrooms closed off & unheated. Even with that the heat pump is running 24/7 with the dreaded "aux heat" showing on the thermostat. It is telling me to start expecting the $300-$400 electric bills..

I considered adding wood heat. I got an estimate from a local fireplace shop to install a wood or pellet stove on the first floor. The work required to place the chimney blew that project out of the water. Nearly $8000...... And I would have the chimney take a chunk out of my bedroom.

Many years ago I built a solar pool heater for a family member. We had no idea what we were doing. We were just "winging it ". We built what amounted to a "ladder" out of 3/4" PVC pipe and fittings and diverted a portion of the flow exiting the filter through the collector and back into the pool. We painted the collector flat black.

i would like to say that it worked perfectly but it didn't . About a month later I had to go back and modify it. The pool was too warm. We bypassed almost half of the collector made it just right.

I was contemplating that the other day and wondering how practical a solar collector on the roof heating water (&.antifreeze) to feed hydronic heaters in the living room. That is where we spend most of our time.

I have been looking and reading about solar heat and I am finding that it has fallen out of favor. Is it simple impractical or am I hearing sour grapes from folks that had a bad experience with the sketchy solar outfits that proliferated back in the 80's and 90's?

We average 176 sunny days a year. Typical sunny Winter days will have high temps ranging from 10F to 40F..

Is there a practical solar solution?

Evacuated tube? Flat plate collectors?

Suggestions?

Thanks!

[peakbagger]

Many have tried few have succeeded in your quest. The fundamental problem is you want maximum heat on the coldest days while the panels want to give you maximum heat on the warmest days. You end up having to oversize everything and then you need to figure out how to waste heat on the warmer days. The far better option is install PV panels and and a cold source mini split heat pump. Cold climate minisplits work down to -12 F but the COP drops so most use them down to about 20 F, They are far more efficient than a standard heat pump as they cut out the intermediate ductwork. You also get AC in the summer at higher efficiency as you cut out the ductwork. If you have net metering available you effectively can store power generated in the summer to generate heat in the winter. I have done that for 5 years in Northern NH in far colder climate and use the mini split for so called shoulder season heating. I use a wood boiler for the colder weather that I expect you don't have at your location. My backup is heating oil but I haven't bought any for five years and go through about 3 to 4 cords of wood.

My guess is you probably have poor insulation in the buried part of your lower floor and a standard concrete slab. They can really suck the heat out of lower level space. If the foundation walls and floor is not insulated consider spending the money on insulating the buried walls and put high density foam on the floor and a floating floor system on top.

[Ampster]

A friend in Hermosa Beach is very happy with his hydronic system using PV solar panels and a heat pump water heater. It is a grid tie system and he banks energy with his utility in the summer and uses it to power the heat pump water heater in winter. His home is all electric.
Obviously he is in a more temperate climate than you so the economics will be different. Another friend in that same city used evacuated tube collectors to heat his hot tub in his all electric home.

[JSchnee21]

I assume you don't have natural gas? Is your entire house electric? Perhaps it's the region of the country, but I'm surprised a home of that vintage wouldn't have either oil, natural gas, or propane heat. Has it always been heated by heat pump? Is it a newer unit / well maintained? Or did they remove the oil tank when they flipped it?

Weather sealing and insulation are certainly the least expensive solution with the best ROI (generally). Have you had a home energy audit? A quality company that specializes in these will quickly help you find leaks, drafts, etc. Is the entire house one zone? (mine is, which sux, but I have gas fired forced hot air (which is cheap to operate) and we predominately live on the second floor -- split level.

Did you have the upgrades done, or was it flipped before you bought it? You'd be surprised what a poor job of sealing/insulating around replacement windows is commonly done. Similarly, if your 2nd floor overhangs the first by a foot or so (never understood why the do this) these ares are often poorly or not insulated at all.

PV could be a solution to offset your electric consumption, but you'd be looking at much more substantial investment -- north of $25K. Geothermal heat would be even more.

You could install supplemental baseboard heat on the first floor (electric or water). A recirculating water system would be the cheapest to operate (on natural gas, propane, or wood) but would have a much more substantial install cost. But electric baseboards are easy and cheap to install (if you can easily pull 240 feeds from a near by electrical panel).

While electric heat is generally "expensive" since you would only be heating the rooms you are in (and not trying to heat your whole house) this would likely be cheaper then running Supplemental (electric heat) on your heat pump.

A relatively new solution (in the USA) is a wood pellet boiler -- This would provide hot water for radiators and potentially replace your electric hot water heater.

https://www.maineenergysystems.com/wood-pellet-boiler/

https://www.pellergy.com/wood-pellet-boilers/

Alternatively, a high efficiency propane boiler with an inexpensive PVC Schedule 40 vent

[bcroe]

Hey Everyone, As Winter sets in my frustration follows...

I live in S.E. Washington State in a 2200sf house that was built in the late 40's to early 50's. It has been
remodeled with double pane windows and 1" of EPS foam board wrapped the exterior walls. It also sports
a 1.5 ton Goodman heat pump.

My frustration comes from trying to maintain 67F in the downstairs of the house. We keep the upstairs
bedrooms closed off & unheated. Even with that the heat pump is running 24/7 with the dreaded "aux heat"
showing on the thermostat. It is telling me to start expecting the $300-$400 electric bills..

I considered adding wood heat.

I was contemplating that the other day and wondering how practical a solar collector on the roof heating
water (&.antifreeze) to feed hydronic heaters in the living room.

I have been looking and reading about solar heat and I am finding that it has fallen out of favor. Is it simple
impractical or am I hearing sour grapes from folks that had a bad experience with the sketchy solar outfits
that proliferated back in the 80's and 90's?

We average 176 sunny days a year. Typical sunny Winter days will have high temps ranging from 10F to 40F..

Is there a practical solar solution? Evacuated tube? Flat plate collectors?
Suggestions? Thanks!

Thermal collectors have difficulty in cold climates, because you get the least heat when you
need it most, and they do poorly or freeze up in frigid weather. Wood burning works, but
requires a constant input of time and labor to function.

I am using PV solar with net metering to solve all these problems. I have no problem keeping
the house at 75 F using mini split air to air heat pumps, for outside weather down to zero F.
When 20 below zero F and colder happen, I may need to use more of my net metering energy
reserve for some resistance heating. The propane furnace only stands by for a power outage
backup. The insulation of 5000 sq ft here is pretty poor, another project.

Your 1.5 ton heat pump is far too small for serious heating, and older designs have rather poor
efficiency. 6 tons in use here. Bruce Roe

[PNW_Steve]

Thermal collectors have difficulty in cold climates, because you get the least heat when you
need it most, and they do poorly or freeze up in frigid weather. Wood burning works, but
requires a constant input of time and labor to function.

I am using PV solar with net metering to solve all these problems. I have no problem keeping
the house at 75 F using mini split air to air heat pumps, for outside weather down to zero F.
When 20 below zero F and colder happen, I may need to use more of my net metering energy
reserve for some resistance heating. The propane furnace only stands by for a power outage
backup. The insulation of 5000 sq ft here is pretty poor, another project.

Your 1.5 ton heat pump is far too small for serious heating, and older designs have rather poor
efficiency. 6 tons in use here. Bruce Roe

Given the performance of what I have now and my experience with HVAC in houses that i have built or remodeled I think that four tons would be plenty.

[bcroe]

Given the performance of what I have now and my experience with HVAC in
houses that i have built or remodeled I think that four tons would be plenty.

For cooling yes, we are discussing heating. I believe 4 tons is about 48,000 BTU/hr. My 2 furnaces
I used to use amount to some 120,000 BTU/hr. And heat pump capability tends to decrease as
winter proceeds. Bruce Roe

[PNW_Steve]

I assume you don't have natural gas? Is your entire house electric? Perhaps it's the region of the country, but I'm surprised a home of that vintage wouldn't have either oil, natural gas, or propane heat. Has it always been heated by heat pump? Is it a newer unit / well maintained? Or did they remove the oil tank when they flipped it?

Weather sealing and insulation are certainly the least expensive solution with the best ROI (generally). Have you had a home energy audit? A quality company that specializes in these will quickly help you find leaks, drafts, etc. Is the entire house one zone? (mine is, which sux, but I have gas fired forced hot air (which is cheap to operate) and we predominately live on the second floor -- split level.

Did you have the upgrades done, or was it flipped before you bought it? You'd be surprised what a poor job of sealing/insulating around replacement windows is commonly done. Similarly, if your 2nd floor overhangs the first by a foot or so (never understood why the do this) these ares are often poorly or not insulated at all.

PV could be a solution to offset your electric consumption, but you'd be looking at much more substantial investment -- north of $25K. Geothermal heat would be even more.

You could install supplemental baseboard heat on the first floor (electric or water). A recirculating water system would be the cheapest to operate (on natural gas, propane, or wood) but would have a much more substantial install cost. But electric baseboards are easy and cheap to install (if you can easily pull 240 feeds from a near by electrical panel).

While electric heat is generally "expensive" since you would only be heating the rooms you are in (and not trying to heat your whole house) this would likely be cheaper then running Supplemental (electric heat) on your heat pump.

A relatively new solution (in the USA) is a wood pellet boiler -- This would provide hot water for radiators and potentially replace your electric hot water heater.

https://www.maineenergysystems.com/wood-pellet-boiler/

https://www.pellergy.com/wood-pellet-boilers/

Alternatively, a high efficiency propane boiler with an inexpensive PVC Schedule 40 vent

We don't have natural gas here. There is a natural gas pipeline that runs through the county and doesn't serve a single customer in the county..

Propane is $3.25 a gallon here so it is not terribly cost effective.

Wood boilers have been around for many years. I remember seeing them advertise them seeing ads for them in MEN in the late 80's.

What I really want to know is if there an effective method of heating with solar.

[PNW_Steve]

For cooling yes, we are discussing heating. I believe 4 tons is about 14,000 BTU/hr. My 2 furnaces
I used to use amount to some 120,000 BTU/hr. And heat pump capability tends to decrease as
winter proceeds. Bruce Roe

Four tons is 48,000 BTUs.

Our heat pump is very low end. It switches to aux heat when the outside temp is around freezing. That turns my heat pump into an electric resistance heater.

[PNW_Steve]

The prior owner had the 1-1/2 ton unit installed. She is a widow and pretty clueless about home repairs and maintenance.

She had the local HVAC guy come out and sold her a substandard system for top dollar.

[Mike90250]

This is about the best of the DIY schemes I've seen

https://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

Also, a high efficiency pellet stove could be useful, and using an external flue outside the wall, instead of inside the house. There is even a no-electric gravity feed pellet heater

https://www.tractorsupply.com/tsc/product/us-stove-gravity-feed-non-electric-wiseway-pellet-stove-2-000-sq-ft

I am very happy with our masonry heater, but you have to build the house around it

[bcroe]

Four tons is 48,000 BTUs.

Our heat pump is very low end. It switches to aux heat when the outside temp is around freezing. That
turns my heat pump into an electric resistance heater.

Sorry for leaving without checking, I should have said 1.5 tons is 18,000 BTU/hr, as you said 4 tons is
48,000 BTU/hr.

Our summer price for propane has been near $1/gallon. Do not buy it in mid winter, an artificially inflated
price may exceed $5. With $0.10 per KWH and 27 KWH equals the heat of a gallon of propane (burned
in a high efficiency furnace), it is cheaper to heat with electrical resistance above $2.70 a gallon.

Peakbagger and I just finished explaining how you can heat with solar, been doing it here 6 winters.
Bruce Roe

[J.P.M.]

Steve:

How much do you want to lower your heating bill by and how much work, both physical and mental (learning) are you willing to put into it ?

Set your goals and remember that you probably want a comfortable living space with a lower heating bill with the lowest capital investment. Solar thermal is one tool to get there, but it's usually far down the list of measures if the list is ordered by cost effectiveness and ease of use.

Before you do anything else, know your starting point. Begin by determining what your current heat loss is, either by doing the calc/est. from a building envelope survey of each exterior surface including floors and ceiling/roofs and an est. of infiltration loss at maybe 2 air changes/hr. Or, do/get the same from an energy audit.

Then, compare those numbers to what you can measure by keeping track of what's used for heat over two 24 hour periods that both require heat but one with warmer ave. outdoor temps by ~ > 10 F. or so. That'll allow you to calc a heat loss per degree day. Multiply that degree day (DD) heat load the diff. per degree of temp. diff. by (desired indoor temp. - design (minimum) exterior temp.) to get a design heat load.

Divide that by 24 for an hourly design heat load.

Divide that by (the %age of the time the heating equipment is designed to operate) for equipment sizing. Add some excess size for the unexpected but not too much.

In comparing what you calc and what you measure, don't be surprised if the calc'd results disagree with the measured calcs by a factor of 2 or more.

That'll give you a back of the envelope est. of what you'll need to stay warm before conservation measures.

Then, start with the least expensive measures first - sealing the building envelope. Add insulation to the attic crawl space and then do the walls as best you can.

How much of your heat load is for DHW ? Get low flow shower heads and insulate the tank and lines. And, if you have one of thos B.S. hot water recirculation systems, for God's sake get rid of it.

After all that, recalc the heat loss and resize the heating plant for the new, lower load.

To your desire to know if solar thermal will work in cold climates: In sunny climates such as yours, solar thermal will probably work a lot better than in climates such as Peakbagger's or where I came from (Buffalo), but in most any case, know that until you get close to superinsulation values, your money will be much more effectively spent on measures that lower the heating requirement of the building than by adding most any solar thermal equipment to it.

Basically, conservation is a lot cheaper than solar for a lot fewer problems. That's just the way it works. I tried it for 20+ years in Buffalo. Insulation and sealing does work. Solar will work some for you, but it'll cost. I'm a big solar fan and thermal was how I started, but I lowered a energy use of an existing 1928 home by 2/3 using mostly conservation measures with about 10 % of that coming from a concerted effort at solar utilization in ways that most folks would soon tire of.

I was at a solar energy conference in the early '80's before PV was more than a distant future dream. It was a world where solar thermal ruled. Anyway, while there, I was talking to one of the solar gurus, a guy by the name of Steve Baer. He was, and I believe still is, a big solar proponent. Anyway, he said something that stuck with me and proved to be true, at least to my experience: The biggest impediment to solar energy utilization for heating a home is not the big oil or energy companies or even the solar naysayers. The biggest threat is that people will learn how much easier and more cost effective it is to insulate and reduce a building load than it is to meet a heat load with solar collectors. If/when they do figure it out, fewer active solar systems of smaller sizes will be the rule, as will passive solar for sunnier areas.

Get the heat load as low as your lifestyle permits before going beyond the simplest (probably passive) solar measures.

BTW, get new windows for aesthetics if you want them, but know that they'll have a long payback if done for energy savings only, maybe even longer than solar thermal which is close to the bottom of the list in terms of cost effectiveness and ease of use.

[peakbagger]

I do have solar hot water on my home. Two big flat plate panels. At best I get 80 degrees over the outside ambient in winter. So on a 20 degree day I get 100 degree hot water. For the heck of it I put in some fin tube radiator on a bypass. It really does not put out much heat. Properly designed and installed radiant floor could work with those low temps and some built in radiant wall or ceiling panels also could work but for most heating systems the temp are too low to be useful.

Mechanical engineers have to take thermodynamics courses and will be familiar with exergy calculations which determines the availability of energy in system. BTUs are a measure of energy but not the availability for it to be used usefully. Folks trying to pull a fast one take advantage of this. There is a big difference between the usefulness of 1 pound of water heated to 1000 degrees F and 1000 pounds of water heated 1 degree yet the BTU content added in either mode of heating is equal. SHW has low exergy. On the other hand PV has a lower equivalent collection efficiency than SHW but with net metering the power is generated all summer and then used when needed in the winter. Depending on where you draw the boundaries the exergy is quite high of the system.With net metering the grid is effectively acting as battery as long as non renewable assets are in the loop. Unfortunately there is no current viable thermal batteries that could store energy for months like PV can be.

On an ideal sunny day with a collector perpendicular to the suns angle at best there is 1000 watts per meter of collector. Multiply by 3.412 to get btu/hr so every square meter or perfect collector may gain 3412 but/hr per meter for perfect panel. Its pretty rare to build a tracking array so the panel angle relative to the sun will change reducing its efficiency. The panels are also radiating heat back to the air while they are collecting heat. For flat panels the break even point is around an 80 degree difference between the glycol temp and the outdoor temp. This efficiency varies with the delta T across the panel. Ideally to reduce the emitter sizing in the house you want water that is considerably hotter than the house temp but that means lower collector efficiency.

If someone goes to the trouble to do the math they will rapidly come to the conclusion that its far more expensive to try to heat a home with SHW than many other options. There were a lot of failed home designs built in the 1970s and early 80s using active solar air heating. Pretty much the standard these days is super insulated design with lots of thermal mass and judicious use of glass to heat thermal mass with overhangs to reduce hot weather heating and very effective thermal shutter or insulated sealed blinds to reduce nigh time heat loss. Deep energy retrofits of existing housing can be done but they have to be done right. Its far easier to do super efficient design in new construction but few developers do it unless there are required minimum energy standards in place that are enforced. They are far better building them quick and cheap to the minimum standard and spending the savings on visual appeal items like granite counters.

[PNW_Steve]

Thank you all for your thoughtful replies.

To answer some of the questions above:

I don't have natural gas. A pipeline runs through the County and does not serve a single customer in the county.

I really doubt that there is any insulation under the basement floor.

Adding PV to heat with exceeds my space and budget.

How much time and money am I willing to expend?

Well.... With the schooling I got from all of your replies, Not enough ..... I see from your replies that solar air or water heater is not practical in my circumstance.

I suspect that if I set out to build a new house and design it to best incorporate solar heat I could probably be successful with supplemental solar heat.


I am committed to staying here for another 2-1/2 years. When I get past that I am considering building another house. I am thinking of something between 600-800sf. Hyperinsulated and built to maximize solar..

Thanks again everyone.