March 16, 2010

2010 Goals: Researching HVAC Systems

As many of you mentioned in the comments to my previous post on this subject, the HVAC (heating, ventilation, air conditioning) system is only part of the home comfort/energy efficiency equation. Insulation is the other factor, and we are researching both. In this post, I'll give you the gist of my research into different types of heating and cooling systems. The ones I chose are the systems which were most feasible of us: electric, combustion based, air source heat pumps, ductless mini-split heat pumps, and geothermal heat pumps. For each one I've included links to more information at the US Dept of Energy Energy Savers website.

Electric systems include electric resistance heating and electric air conditioning. Heaters can include electric furnaces, base-board heaters, space heaters, and some radiant heat systems. All air conditioners are electric, no matter what heating system they come with. The advantage to electric heating is that almost 100% of the electricity is converted to heat, so it's efficient. The disadvantage is that not only is it the most expensive way to heat and cool, but also electricity is often produced from oil, gas, or coal generators, which are not efficient as they produce the electricity itself, not to mention they are fossil fuels.

To read more on these systems, click here.

Combustion based are your oil, gas, and propane heaters, often packaged with electric AC. These systems require an open flame to produce heat and hence a pilot light. These are of course, safety concerns. In addition to heat, they produce waste products such as carbon monoxide, requiring them to be vented to the outside. While they are less expensive to run than all electric, they require a lot of maintenance. They are less efficient, typically having an Annual Fuel Utilization Efficiency (AFUE) of 80%. This means that only 80% of the fuel is converted to heat. To be Energy Star rated, a system must have an AFUE of 90%, and these are considerably more expensive as you can imagine.

For more reading on furnaces and boilers, click here.

Air-source heat pumps transfer heat from outdoor air, rather than create heat from a fuel source. This makes them more economical to run. While they can be efficient air conditioners in the summer, they do not work well as heaters if outside temperatures drop to about freezing or below because the air is no longer warm enough to transfer heat from. Consequently most air-source heat pumps in our part of the country are duel-fueled, equipped with a gas heater as well. Gas kicks in when the outdoor temperatures are too cold. Other alternatives would be electric heaters, or as in our case, a woodstove.

Air-source heat pumps have two efficiency ratings, the Seasonal Energy Efficiency Ratio (SEER) for the air conditioner, and a Heating System Performance Factor (HSPF). The most efficient ones have a minimum SEER of 14, and a minimum HSPF of 8. With both ratings, the higher the number the better.

For detailed info on these, click here.

Ductless, mini-split-system heat pumps are air-source heat pumps which can be retrofit to a home without ductwork. After the outdoor unit is installed, 3 inch pipes carry the wiring/tubing to indoor units, which are installed about a foot from the ceiling. They make it easy to zone one's home, but the indoor units themselves are pretty conspicuous and ugly. To me, a cooling source near the ceiling makes sense, but heating doesn't. Why? Because heat of course, rises and the ceiling is not where one wants the heat in winter! Strong blowers can help, but we had ceiling vent registers when we lived in the apartment and didn't think the heat circulated well.

For more information on these systems, click here.

Geothermal heat pumps, also work on transfer heat, but their source is either the earth or water, rather than air. They are least expensive to maintain but most expensive to install, primarily because of the several hundred feet of tubing which needs to be either buried 5 to 6 feet in the ground, or submerged. They have the least impact on the environment of all the options, and the longest service life, something like 25 to 30 years for the unit and 50 years for the tubing.

Click here for more information.

We are not considering radiant heat, as this would be difficult and expensive for us to retrofit (as in tear up all the floors). Nor solar, because we do not get enough sunlight during the winter for it to be truly useful nor worth the expense.

We were able to attend a home and garden show earlier this month and talk to a lot of both HVAC and insulation folks. The next step should be to have a variety of them come out, and give us their spiel and free estimate.



17 comments:

Renee said...

What type of heating/cooling do you have?
How do you like it?
If you could change it, what would you choose?


we have a gas furnace (that has an electric pilot, so no continual flame) with electric A/C and a humidifier attached.

While the system does a okay job at heating and cooling the house it seems as if folks don't really think it through. The house has heat registers in the floors which works well for heating, the same registers in the floor are not so efficient for cooling the house.

to make it work a bit better we shut off the upstairs vents in the winter and the downstairs vents in the summer. I think the best idea would be to move the thermostat out of the foyer where it gets affected by the sun coming in, but alas DH doesn't want to do the drywall work to move it.

In my perfect home we would have radiant floor heat, but I'm not sure how to cool it, probably have registers in the ceiling.

Alison said...

I think this is one of the ways that the UK is vastly different to the US. A/C is *not* standard in private homes here; typically there are only a few days (and probably a few more nights!) each year when it would really be used. We have a portable A/C unit that gets dragged out of the under-stairs cupboard if things get hot, and that's only a very recent thing. For heating, we have the standard UK 'central heating' - gas boiler which heats water-filled radiators in each room. We had the boiler replaced a few years ago for a smaller, more efficient model, and have an active thermostat controlling the whole system, plus thermostatic valves on all our radiators now. Older central heating systems don't really have thermostats; they're on or they're off, usually on a timer basis. My parent's place is like that. Our new system is pretty much 'always on', but you set the minimum temperature and it only becomes active if the temp dips low enough. We do set different minimum temps for night/day etc.

I've never heard about geothermal heat for private homes before. It's a very interesting idea!

Theresa said...

Oh we would have loved to put in a geo thermal heating system, but it was terribly expensive.
We have dual fuel sources. An outdoor wood fired boiler that heats the water that then recirculates through our radiators and is thermostat controlled from all the house thermostats and the regular oil boiler. It is easy to switch between the two when we need to. I like the radiant heat a radiator gives as compared to blowing air ( and dust and dog hair) around. The radiators are from Germany, slim, wall mounted and quite nice compared to the old finned variety.

Leigh said...

Renee, radiant floor heat is exactly what Dan would like too. We actually though about it and discussed it but really, it's more practical for new construction than an old house like ours.

You are so right about register placement too. That's a problem either one season or the other.

Alison, that is so interesting about heating & cooling in the UK. Who would think to ask "So. How do you heat and cool your house?" But thanks to blogging, topics like these are a peek into how others in the world live.

In the northern US, a lot of homes don't have AC. But in the south, with our heat and humidity, you couldn't' even put a home on the market without it.

There aren't a lot of geothermal units in private homes in the US. The unit itself is high end, but it's the excavation required to bury the coils that cost the most. Even though this is the most energy efficient system and would be our preference if money were no object, really, this system is out of our financial reach. I only wish we could get grants to install them, like they can in Canada and the UK. A tax rebate is nice, but doesn't help those who have the upfront cost to begin with.

Theresa, dual really sounds like the best way to go. Excellent point about the blowers that are needed for central heating and cooling. Since we already have that in place, it's a logical direction to go itn, but we haven't made any decisions yet.

Julie said...

We have to gas units in our house but we don't use them we heat with pellet stoves. We have AC but only use it at the end of July first of August. We love the heat so we only turn it on for Paisley while we are at work.

Woolly Bits said...

we have two solid fuel stoves with backboilers, which don't only heat the water, but also two or three attached radiators. we also have one without backboiler, which we hardly ever use, because it's never cold enough here:)) even during this exceptionally cold winter (for us!) we didn't need it. cooling on the other hand - that would be a laugh, because we only get temperatures over say 24 or 25 deg. C on maybe 1 or 2 days a year - if that!:)) like Alison in the uk said, A/C is not common over here, not even in germany, where the summers are far warmer. with fuel prices that high people tend to rather "sweat it" than pay even more for cooling instead of heating:))

Benita said...

We have a propane furnace and central air. When we built the house, propane was inexpensive - not anymore. My monthly budget has gone from $50 to $300. AND we keep the furnace set at 50 at night and 55-60 during the day in the winter.

I'd love to have a combo of solar and geothermal.

Leigh said...

Julie, you are so fortunate not to need your AC all that much. Actually, I only turn it on when it gets unbearable in the house. And last summer our temps didn't get over 90 F, a blessing!

Bettina, this is interesting. I wonder if folks in the US will use air conditioning less considering our economy. Prices are going up and folks have less money to spend and have to make harder choices. I do find though, that once people get used to a certain lifestyle, it's harder to cut back than to start will less to begin with.

Wow, Benita, that's a real jump over the years. I worry the same will happen with oil and natural gas. Also electricity, because too often it's generated from oil or gas sources. Geothermal truly seems the best way to go, but who can afford it???

Anonymous said...

Whatever your choose, if possible a tankless water heating system might be of some interest. It does away with the water heater. Also, a friend once commented that electric baseboard heat was a good way to go if money was an issue. Cheap to get in and can be turned on/off as needed. The cheap part would free up cash for other parts of the system. I have no knowledge of the cost effectiveness on my own. The downside is you have the baseboards running along needed baseboard wall space. Also, you mentioned radiant heat was out, but aren't there some sort of mesh-like electric 'rugs' that can go under tile, such as in baths/kitchens? --Sue in MA

bibliotecaria said...

What about hydronic heating, but not the radiant floor type? Rather the baseboard/radiator type? (I've wondered about that one due to allergies.)

Dorothy said...

Just a query about the 100% efficiency you say electric systems have, this ignores the energy loss in transmission of the power from where it is generated to your home, typically I think the figure is about 30%.

If you insulate first would you be in a better position to assess the heating capacity required, or will the people doing the assessment factor in the effect of future insulation? Good idea to get lots of different assessments.

I was interested that you mentioned gas. Do you have a piped gas supply as we go via a national grid, or would you have to get gas delivered and store it in canisters?

Dorothy said...

Just to add - like Alison and many people in the UK we have a gas fired central heating system. Ours is carefully monitored & controlled by an electronic control system with several separate zones in the house that can be set for different times on/off and different temperatures (plus other less relevant features). This is a sophisticated controller not normally found in private homes as my boyfriend designs / manfactures them and naturally we have a test unit running at home. It does things like assess out door air temperature and switch on early if necessary to have the space at a given temperature for a given time of day. The same system provides domestic hot water. This customers for this type of controller include local councils, schools, various kinds of public buildings who can potentially make huge energy savings with a really good control system.

As secondary heating and very useful in powercuts (as the gas central heating boiler requires electricity for ignition) we have a dual fuel stove that will burn wood or coal.

Leigh said...

Sue, yes, tankless water heater is on our list! I hadn't heard of the electric rug pads! Very interesting. That may be a possibility, though I'm not sure where at this point.

We have talked about baseboard heaters. I like the idea that they can be used on an as needed basis for zoning the house. We consider them for the bathrooms, but in the smaller bathroom, there's not even room for that!

Bibliotecaria, I've never heard of hydronic heating. Thank you for mentioning this. I will have to investigate further.

Dorothy, you are correct about the inefficiency of electricity being delivered to one's home. The 100% efficiency refers to the heat produced at site. Your point is a good one, because it means electricity as a total package (creation and delivery) is extremely inefficient.

We're leaning more toward insulating first, as you mention. The very cheapest thing would be to have the oil furnace reinstalled and then work on not having to use very much of it!

Speaking of that, we have an oil tank, buried in the ground, which means we have to take delivery to get the tank filled periodically. Propane works the same way. Natural gas, however, is usually piped into homes via the local utility service. It is possible to buy it by the tank too, which some people do for things like gas stoves.

Interesting about your control system. How fortunate to have it in the family! Sounds like an idea solution to keeping cost and energy consumption down.

Anonymous said...

We had an 1,000 gal. underground oil tank (live in New England), but banks stopped loaning on homes with these a long time ago, at least 15 yrs before the current banking crisis. So when it was time for a new oil furnace/boiler, we had it removed (thankfully, no leakage, which would have required a full-blown and expensive environmental clean up even for a tiny spill) and two 330 gal. tanks installed in the basement. We don't get quite the same discount on oil deliveries now, but at least the tanks are double insulated. We have old-style upright solar panels to pre-heat the hot water, as well as the tankless hot water system. Together with the well and septic system, we're pretty self-sufficient (except for electricity, that is).--Sue in MA

Leigh said...

Sue, I appreciate this. Knowing what other folks use, the problems they encounter, and their solutions is very helpful. Interesting about the mortgage loans.

Do you have any plans to supplement your electricity with wind or solar? We've been assessing for both of those, but aren't very hopeful that the amount of sun and wind we get would even begin to offset the expense of installing them in the first place.

Anonymous said...

Re installing more solar or new wind. Wind is out. I'm not a fan of it due to damage to avian wildlife, plus all our property (2 acres) is wooded except right around the house. Less than half-a-mile away there is one - about $200K to install, even with a grant. Way too expensive, and that was in open area on flat ground. Same would be for more solar, I think. You have to look at the payback time, and I'm not sure it would equal the years left in the house for us. I"m an advocate of solar on roofs of all new construction. After all, those roofs just sit there doing nothing but providing shelter. They could at least be twice as useful. [grin]--Sue in MA

Leigh said...

$200K!?! Good grief. I would be interested in the details on that. I've compared our monthly kilowatt hours to available windmills, and the only one that could make a difference was $10,000 just for the windmill itself. That didn't include set-up, etc. They definitely seem overpriced. For us though, I don't know if we actually have enough wind to have one make sense. Ditto for sun and solar. Still, solar panels on new construction makes sense, Sue. Every little bit helps.