After paying over $1,600 in gas bills (radiators) from November to April, I’m having my old house retrofit with a heat pump and ductwork. I’m also planning to insulate the walls (no insulation now), and I have a couple of questions.
I’m getting an estimate from a reputable company here in town (Louisville, KY – Allgeier), which looks to be in the $12 to $15K range, depending on several options. According to my very-energy-conscious co-workers, this company does a very good job of design that results in a comfortable and efficient system throughout the house. So, I’m inclined to go with them instead of someone who will tell me that since I have a 2,800 ft² house I should buy a 4 ton unit just in case so that it will not be undersized. That being said, does this range seem high? They’re suggesting the following:
– 14 SEER Westinghouse HP, ~$3,500 installed
– Two-stage Westinghouse 80 AFUE furnace (backup for HP) with variable speed fan, ~$3,500 installed
– Pneumatic dampers – $1,500 – $2,000
– Ductwork – $3 to $6K (big range due to uncertainty about location of ducts; will probably be closer to the lower end).
I’m considering the upgrade to a 90-92 AFUE furnace – mostly so that I can use PVC to vent the combustion gas and avoid the stack on the side of the house. Winters are fairly mild here, so the furnace will fire only about 14% of the year.
I would also consider upgrading to the 16 SEER unit, but I’m not sure what the payback would be.
The ductwork is the big variable. The air handler will be in the basement, with two trunks running straight up to the third floor attic space. First floor ducts in basement, 2nd/3rd floors from the attic.
In the “more-bang-for-your-buck” category, I would like to try blowing insulation into the walls, but I’m not sure how well the unit from Home Depot will perform. Anyone tried it in this application? The insulation they sell (Cocoon) has directions on their website that seem simple, but I think that there is a whole thread on that going in the General Discussion forum. I’ve gotten a quote to do it for about $1.30/ft²; the Cocoon price (uninstalled) is closer to $0.23/ft². Difference is a couple thousand dallars.
Some of this is probably already in some threads somewhere; may be easier to just point me towards them if you know where they are. Every search I’ve done brings up too much info.
Replies
Do an advanced search (above the message list) on Dense Pack and maybe also Denspak.
You will find several discussion on using blowers to dense pack celulose into cavity. Most will be behind a "net" in open walls. But also some on doing it in existing walls.
And also do good job of air sealing, specaily in the attic. That will get you a good bang for the buck.
And do all of this before you get the new HVAC so that it properly sized.
I sympathize with the energy bills, but having had radiator heat in my last house for 14 years, and forced air in my new one, I'll take radiators any day for heat. And we are not in a very cold climate (about like yours).
I'm not sure about the payback for 16 SEER AC units, but I do know that the technology for the higher SEER units (I think it is reciprocating for new and scroll for old), but I might have it backwards) is WAY more quiet. I think it starts at 14 SEER, at least in the line we got.
One positive we did find for forced air heat is humidifiers. We went for the units that have their own fan, which require a seperate power source (just a plug). I found a setting of about 45% for Columbus was pretty good last winter. This unit has an outside sensor that increase the humidity slightly when the temperature falls.
If you have radiators in the house now...
Why not go with some kind of water based system instead of changing to air?
Just replace the boiler with a high efficiency unit as you had already planned.
You could either stay with substantially the same radiator system you have now or change some or all of it to in floor heating or just more modern radiators.
I was starting with a water system I don't think I would change.
Densepak cellulose can do a very nice job on your walls if you get every single cavity. That means, in practise, that your drywall or plaster or whatever is there is going to require a lot of patching by the time you finish. Another caveat. Make sure you have some kind of exterior sheathing between the stud framing and the brick veneer on your house. Cellulose in contact with brick magically transforms into a ... sponge. Which is really another name for mold farm in this application.
As far as using cellulose in your attic, there are relatively recent threads on that all over the place.
Read the article on "Fixing a cold drafty house" in the energy efficiency section of this site.
Previous homeowner in my house had torn out the boiler and rads and put in top of the line 90% furnace and a/c just before we moved in.
First thing I did? Installed condensing boiler and brought in salvage radiators. Cant beat the comfortable, even heat, and the savings. And the radiant floors...ahh.
It seems like you are pinning the high heat bills on the rads, where obviously you have an inefficient boiler. The newest boilers have what's called a turndown ratio, where they can just simmer, instead of running at full fire on milder days, like your current boiler. Combine that with outdoor reset, and you will really save money.
Now, if you want central air, I understand its an alluring package to drop in the furnace.
But don't do it!
Not that anyone ever listens when I tell them not to go w/forced hot air. Just have to send you this out of habit :)
As was already posted, hold off your hvac upgrades until you've done your airsealing and insulating, then have your company do a heatloss calc reflecting what was actually done. You will save some on the equipment downsize, but will gain alot more in operating costs down the line.
I do not plan on ripping out the boiler (water heater). I like the look and feel of radiant heat as well - just want something more efficient. I'll probably still run it a few days a year to keep it from degrading too rapidly. It's only two years old - previous owner replaced it, but still it's only about 80% efficient.
No turndown on my boiler though, fires at 180,000 Btu's. However, I can't justify replacing a two-year old boiler with a more efficient model when HP's achieve 200% efficiency, especially when electricity is as cheap as it is in Louisville.
I planned to install a coil in the air handler and use a loop from the boiler instead of buying the furnace, but the price difference between that route and an 80% furnace was only about $100, and I'd have a more complicated and less efficient system.
The A/C is also a big driver. We have two window units that do a good job, but would rather have a central system. Can't hurt the resale value either.
R.e. holding off, I've let them know my plans, so they are sizing accordingly.
Thanks for the responses; what about the prices? Do they seem reasonable?
You might want to look at seeing if the burner can be replaced with a smaller one.
Your boiler is almost certainly way oversized. I can't see how an installation that far south could require 65BTU/(ft^2 x hr) unless you're warming multiple glass houses.As far as paybacks go, I have seen multiple data points at the Wall on HeatingHelp.com where homeowners and contractors reported 40%+ gas savings when converting from a 80% cast-iron, fixed-input unit to a modulating, condensing boiler like a Munchkin, Vitodens, Ultra, etc. This is on a heating degree-day adjusted scale...Plus, considering how badly your boiler is probably short cycling, it's doubtful it ever reaches an efficient firing condition. The only way to improve it's performance is the addition of a well-insulated buffer tank that then allows longer firing periods. However, your best solution is probably to do the following:1) Get a room-by-room heat loss/gain calculation done.
2) Investigate your options in the light of the results. Incorporate the coming insulation package, also consider retrofitting good storm windows like the Harvey Tru-Channel variety. Even with historic sashes on the inside, the performance is close to that of a thermopane window.
3) Consider retrofitting a condensing, modulating boiler. Such a boiler can heat your hot water (via an indirect water heater), heat the radiant floor circuits, and also heat the other areas of the house with a hydrocoil.I bet that after your house was insulated that you'll require less than 20BTU's/(ft^2 x hr) on a design day. Our reasonably-well-insulated house is projected to lose 16BTU's/(ft^2 x hr) when it's -15*F outside. I doubt KY ever gets that cold. If electricity is very cheap in KY, your other option is to keep the boiler and install a good heat pump to act as the first stage of the system. Then, when that is exhausted (size it to the lower of the heating/cooling load), you can supplement with the existing boiler.
My suggestion is keeping your radiators, possibly upgrading your boiler, and insulating using blown in cellulose.
For A/C, have you had anyone price a mini-duct system like Unico/Spacepak?
I'd say more, but gotta run!
Aaron
I looked into the high-velocity units last year and had the same company give me an OOM quote. The downsides were a bit too worrisome:
Was a bit more expensive
Also somewhat less efficient
Stories about air whistling through the house worried my wife
In the end, we're not adding any soffits to run duct, and we're only losing about 8 ft² of space in one room on each floor for the trunks. So, the new system will be pretty un-noticable.
That would be a good deal where I live, depending on what what's involved in running the ductwork, which is the hardest part. Enjoy your A/C!
FYI, I just installed a deep pleated media filter. Awesome. Its over 75 sq.ft when "unraveled." Keep in mind that the filter that comes with your unit is just there to protect your equipment, and get some real filtration while you're getting your new equipment. Mine was an Aprilaire Spaceguard.
Philly is generally more expensive than the Ville, but thanks for the feedback. I trust these guys, so I have not gotten any other quotes.
The salesman did offer to throw in a year's supply of some better filters. I assume it will have an odd dimension or will do a really good job so I will be inclined to buy them next year.
Thanks again everyone-
Have most of the HVAC installed - they turned it on today. Have a couple of questions...
1. The return air "ducts" in the basement are all sheet metal while running perpendicular to the joists, but use the joists and floor above as walls while running parallel to the joists. I can live with that, although I am somewhat surprised that one of the "premier" contractors in town would not use metal on all sides. Is this SOP for retrofits? What about new construction?
2. There is quite a bit of electrical wiring in at least one of these joist spaces - some crossing it and some running along it. Since it is pre-existing, is it against some code to use the space as a duct or is it grandfathered? I know that a fire could be bad news r.e. vapors in supply venys - does this apply equally to returns?
Oh, yeah... The insulation folks started today as well. Very nice couple, great price - <<$3,000 to do all the walls (2,800 sq ft home, 140' x 25' of exterior walls), attic and third floor below the flooring, spray-on in the crawlspace, and foam-board the external cellar door. Made a heck of a mess blowing into these old walls, but I know it will be worth it.
"2. There is quite a bit of electrical wiring in at least one of these joist spaces - some crossing it and some running along it. Since it is pre-existing, is it against some code to use the space as a duct or is it grandfathered? I know that a fire could be bad news r.e. vapors in supply venys - does this apply equally to returns?"What kind of wiring.If it is romex you can cross a bay with HVAC duct, but I think only return air. But not run with it.Just found the section and for bays used for HVAC (either hot or return) you can cross it perpendicular.You can run wire in the bay inless it is MI cable, MC cable (with an non-metalic jacket), AC cable so labeld, or one of the metalic conduit systems.
The wiring is romex that I've installed over the last year. Most of it is crosses. There are a couple of runs, but only a couple of feet. There is one return vent immediately above my panel, so there are a lot of wires running along that bay. They have not run the duct to it yet. I'm going to call the installation manager to make sure that they run a duct instead of using the cavity.
Thanks Bill-
Lew, I would before you change anything, work on the envolope, insulate, insulate, insulate. Then bring in a good boiler man and do a heat loss & check out your system. That 180,000 btu for 2800 SQ could be oversized. There is no quick rule of thumb for sizing a boiler, a good heatloss is the only way. Most older home were way oversized to make up for lack of insulation or bad windows, when energy was cheap, and then when the boiler is replaced the installer puts in a larger unit, bigger is better thinking. Not so!! You need a starting point, heat loss. Slantfin on there web site has a free cd for heatloss, will get you close but doesn't replace a professionally done study. I have approx. 4,000 sq home with a 135,00 output Weil-Mclain boiler, poor insulation and I still thing I am a bit oversized, too many cycles per hour, here in MI. With out a heat loss your just guessing!!!
Thanks. I'm pretty sure that you're right about the heat loss. Zero wall insulation on the original structure (1910) and first addition (probably 1920-1940). We've had someone start blowing in cellulose - they should have the walls finished by the end of the week. Also doing some adhesive-blown stuff on the "cellar" spaces (above-grade only per mfr. recommendation). The place should be relatively tight by the time they get through.
As far as the heat loss goes, I'm not really confident of the calculations. I did a heat HAIN calc to size the HVAC last year - came out to over 8 tons (but I don't know what I'm doing). The HVAC installers did one as well and came up with about 6 tons before subtracting for the proximity of neighboring houses and trees in the neighborhood - both of which provide a great deal of shade. Anyway, we had two window units cooling the house - very comfortably last summer and this one which has been rough so far. The combined duty on these two units is 2.5 tons. I told the HVAC guys that I would NOT put a 5-ton unit on our house, would be a waste of money. We agreed on a 3.5-ton unit with the stipulation that on the "peak" days we should not expect that the house will remain at 72° - it may creep up a bit. I can live with that for the 10 peak hours/year.
I will probably have someone give me a recommendation on the boiler this fall. Too many other things going on right now. I think someone suggested a smaller burner. The HVAC guys suggested modulating the boiler temperature setpoint based on outside temperature, which sounds like a good idea too.