Budget conscious upgrades for a not so good house
I need to replace an old gas water heater and HVAC. The air handler and water heater are installed in the garage. We have a household of 4 people (2 adult, a teenager, and one soon to be teen). The house was built in 1991 and it’s around 1900 sq ft with more sq ft upstairs (room over garage).
I’ve been working on sealing the crawl space and will finish and insulate the perimeter when I can get some more dust masks. The windows are old cheap metal framed single hung units. It’s a two story with a significant stack effect. There’s a lot of upgrades I want to make, air sealing, windows, doors, insulation, etc….but as most normal people I’m on a budget and it will take time.
The HVAC unit is currently a single zone 3.5 tonne unit for 1900 sf. It took a while to find someone who actually knows how to size things and they are looking at a 2 tonne unit with a variable speed blower. A second thermostat will be installed upstairs with a damper to control air flow. The current ductwork will be reused due to budget which really sucks as it’s ductboard configured for a 3.5 tonne unit (so it’s too big), but that’s pretty much what I think I can get at my budget.
My question on HVAC is should I go all electric or stay with gas heat? I don’t have solar and have no plans or budget for going solar for electricity generation (just an FYI).
The other thing I am going to be replacing is the old gas tank water heater. I heats water fine, but it also intermittently spews out a black, oily, residue. I’ve read a bunch of articles here and on other sites and it looks gas tank water heaters are not really very much in vogue. I say that because I can’t really find articles saying much about gas tank water heaters at all.
Is replacing my existing gas tank unit with another gas tank unit a really bad thing environmentally? I read Ted Clifton’s article from 2011 and it kind of made sense and then after reading the comments it kind of didn’t. That was back in 2011….is there any new consensus on gas tank water heaters?
In my last house, which I built with SIPS, I had a marathon electric tank and it worked well and was fairly efficient. I’m not sold yet that the HPWH’s are going to last 10+ yrs without significant repair cost along the way. Any input on the durability of HPWH’s? I’m also leary of tankless for the same reason…durability. My in-laws live in Europe and have a gas tankless an no problems. Is the technology the same here? Will it be just as durable?
Matt Risinger has a video where he indicates that the key benefit of tankless is the unending supply, not cost savings. Anyway…those are my quesitons. Should I go all electric for HVAC and should I just replace my gas tank with another or pursue some alternative…and which?
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What part of the country do you live in? How cold does it get in the winter? Did the HVAC company do a Manual J load calculation, and if so what were the design temperatures for 1% and 99% temperatures? Most duct systems are actually too small or restrictive, so that part might not be really bad, but you should measure static pressure on the old system just to see, as the duct system can make a big difference in efficiency delivered by a new unit. At least, Adding a second return in the master bedroom usually makes a difference on airflow and efficiency.
I live in East TN so winter's are mild and electricity is relatively cheap for now. The HVAC company did measure the house and do a manual J. I haven't seen the calcs to know the 1% and 99% details. Though there is currently only 1 thermostat there are 2 returns.
I switched to a Rheem heat pump water heater and a Rheem RP17 3 ton Heat Pump from a 5 ton AC and 100k 80% furnace. I’m very happy with the performance and especially the comfort. We have 4 kids at home so we did the 80 gallon Rheem with higher cop of 3.7 and able to handle large family in Heat Pump only mode. RP17 is a 3 stage in cooling, 3 stage plus overdrive in heating, inverter compressor heat pump. It is a good value for a multi stage 18 SEER system. Overdrive in heating mode allows it to meet nameplate Btu output down to 17 degrees F. I would recommend zoning a 2 story house with zone dampers, but Never use a bypass duct to maintain airflow or lower static pressure. Instead adjust the stop on your dampers so they’re always cracked open a little, so if upstairs is calling for AC, some (20% or so) of the air will still go downstairs. Like Akos mentioned good airflow and low static pressure (like back pressure) makes the fan motor more efficient and draw less watts, and airflow is what moves heat in or out of the indoor coil, making it more efficient. Rheem offers a 21”x21” indoor air handler cabinet that moves more air with less fan watts than the 17”x17” I had to use because of AHRI # match for a rebate program. To fight the stack effect, and improve comfort, there’s no better DIY than air sealing the attic floor. It’s really cheap as a DIY, just buy a gallon of mastic at a HVAC supply house for about $12 then use cheap .99 cent paint brush (trim half the bristles length off) to paint top plate/drywall seams, wire and pipe holes in top plates, any other holes you see. You can also seal your duct work if you have to reuse it.
Have you flushed out your HW tank? Just open the drain and take out a bucket or so or until it runs clean. Replacing the tank if and when it starts to leak is probably your best and cheapest option. That black residue may be coming from the piping itself. Try turning off your water main, draining down the system and then turning it back on a couple times to loosen up and flush any debris that may be in the pipes.
As far as your HVAC, once you change over to a new furnace, register and return grates can be sized and changed accordingly to get the proper flow without removing existing duct work.
Andrew,
Martin has an article on comparing the costs of natural gas and electric appliances (https://www.greenbuildingadvisor.com/article/heating-fuel-cheaper-electricity-natural-gas). It might help to inform your decision.
Taking a quick look at your climate, you are definitely in the area where heat pumps work very well. Even without cheap electricity, the operating cost of a right sized heat pump in those milder climates would be less than gas.
I would get somebody other than the HVAC company do your heat calcs. I would question that a 2000sqft house with single pane windows in your climate needs 2 ton unit.
There is nothing wrong with oversized ducts unless they are in the attic. Oversized ducts reduce flow velocity thus they are quieter and the blower in the furnace uses less power.
For energy imporvement, your lowest hanging fruit is air sealing the house, getting a blower test would let you find some of those big leaks and also give you an actual number for air leakage to properly size your HVAC.
Storm windows might also be worth it as a budget alternative to replacing the existing single panes.
HVAC in the garage is not the best for indoor air quality, you really don't want any of the fumes from there making it into your ventilation. If this can't be easily changed, make sure the ductwork and furnace is well sealed up.
If moving the HVAC is not an option, building a small utility room around the furnace and sealing this up is a big improvement, plus you would be also loosing less heat to the garage.
Akos I would be interested in see math that will show a heat pump can cost less than a 96% gas furnace for a house.
1 Supplied with gas at the averaged US$2.57 per million British thermal units (MMBtu) in 2019
2 Supplied with electricity at the averaged TN $ .1079/kWh
3 For a house in Tennessee
Walta
If your gas is that cheap (less than a penny per kWh equivalent), then no way.
My natural gas, which I though was cheap, works out to around $0.04 per kWh equivalent. A heat pump with a COP between 3 to 4 would come in less than natural gas for me. A 2 ton Carrier greenspeed would easily hit those COPs in warmer climate.
There is also a benefit to higher efficiency heat pumps when it comes to cooling. For example, for me, the cooling costs are about 40% less compared to a standard non modulating AC.
What do you mean by a COP?
My utility rates look a little higher than yours.
Electricity has a monthly customer charge of $16.67 plus 0.08885 per kWh
Gas has a monthly customer charge of $10.27, a facility charge of 9%, and All kWh per month 0.06475.
COP is coefficient of Performance. It refers to the efficiency of the refrigerant cycle to move heat, rather than create heat, in this example COP of 3 equals moving $3 of heat using $1 of electricity. So if nat gas was 3 times cheaper than electricity, the cost of heat produced by a heat pump with a 3.0 cop would be equal to a 100% efficient furnace, which the most efficient offered now is 98% I think. So if electricity is twice the price of gas, but you have a heat pump with cop of 3.0, it would be cheaper to use the heat pump. (And cleaner) If you could go all electric, maybe you can eliminate that gas fixed service charge too
If I read your bill correctly, gas is just slightly less expensive than electricity. If this is the case than a heat pump is a no brainer, it will be much cheaper to run.
If your water heater is dying, I would replace with a heat pump unit, if you have a lot of people in the house, go for a large volume one as recovery is slower than your existing gas burner.
Once either your AC or your furnace gives out replace it with a correct sized modulating heat pump. Make sure the installer also updates your thermostat and wiring, I've seen multi stage units wired to single stage thermostat. It works but much less efficient.
P.S. You can also get rough COP from HSPF by dividing it by 3.4. So a HSPF 12 unit is around 3.5 COP. One thing that is never taken into account is that your existing gas furnace blower consumes a lot of power, but when it comes to heat pumps that blower power is part of the HSPF/COP measurement. In effect a COP 3.5 unit is actually 5% to 10% more efficient once you take the blower power consumption out. This can make a difference when comparing gas VS electric.
I like my heat pump but in most locations city gas is so very cheap and makes very warm air, it is very hard to say no in terms of dollars and cents or comfort.
Your local rates make all the difference. I asked Google and now I wonder if I got the wholesale price and not the retail.
Walta
Andrew
Do you have aluminum framed windows? If so you are the rare case where replacement window may make financial sense if you will be staying for the next 20 years.
Is your duct work in the attic? A very bad idea but happens often.
Walta
The windows are some sort of metal framing, likely aluminum. I mentioned previously they were single hung, someone misinterpreted that as a single thickness of glass. There are two pieces of glass with a spacer. Single hung refers to the operation of the window. In a Double hung the lower portion can raise and the upper portion can dome down. In a single hung the lower portion can raise, but the upper portion is fixed in place.
Ductwork for the first floor is in the crawl space, encapsulation in process. The second floor ductwork is run through the floor joists between the 1st and 2nd floors.
Attic insulation is not anywhere close to thick enough, but until I can do some air sealing (or hire someone) then it is what it is.
Hi Andrew.
I have yet to hear anything but positive feedback on heat pump water heaters. I installed one in my own home and it performed great (I sold the house after having it for 4-5 years, so can't comment on long-term durability). Have you read this: Choosing an Efficient Water Heater?
I grew up in a house with aluminum windows. We would often have inch thick ice on the window frames. Do you see ice on the indoor window frames when it is below zero outside?
It is easy to tell aluminum from most other metals as a magnet will not be attracted the aluminum.
I read your answer 3 times and am still not sure if the windows in your house are single pane or dual pane. If they are dual pane replacing them is unlikely to financial sense.
That is good news about your duct work.
Encapsulation is a buzzword that pushes my buttons. You can vent a crawl space or condition it. Encapsulation implies the crawlspace is somehow separated from both the indoors and the outdoors. It seems likely your ducts will leak enough condition your crawl space.
Walt
In East TN it rarely gets cold enough to have ice anywhere. I'm not sure it has been below zero in the last 5 yrs that we have had the house. The windows are dual pane. It might be good news that there is not ductwork in the attic, but it's pretty close to as bad to have it in the crawl space.
What I mean (and I think most people mean) by encapsulation is that I am not just putting a vapor barrier laid on the ground, but am sealing the seams (with Huber Zip Tape) and running it up the sides and sealing it to the concrete block (I forget which adhesive I am using. I think it's a loctite brand. It's low VOC and will bond concrete to plastic). Eventually I plan to seal the crawl space vents, insulate the perimeter, and put in a dehumidifier. Not everybody insulates or puts in a dehumidifier, but cest la vie. I'm not done, but I'm out of masks and its pretty dirty and dusty down there so until I can get some more it is what it is.
I thought I'd mention my local gas and electric rates. I understand that these will likely go up over time, but this is current.
Electricity has a monthly customer charge of $16.67 plus 0.08885 per kWh
Gas has a monthly customer charge of $10.27, a facility charge of 9%, and All kWh per month 0.06475.
My utility bill includes, gas, electric, and water. August of last year was $235.32 electric and $15.60 gas. January was $126.78 electric and 77.10 gas.
I put this update on the Q& A spotlight article, but thought I'd post it here as well.
Here's where things landed. We are going with a Carrier 14 Seer Single speed 2.5 ton heatpump and a 92% gas furnace to have a dual fuel system. I doubt the furnace will be used much, if at all. In the long term the gas just isn't used then we'll just have the gas turned off so that we don't have the monthly fee.
The HVAC company I landed with seems to know their stuff and felt I'd be better off putting my money into more airsealing, windows, and insulation instead of a multispeed system that would drive up the replacement system cost.
IF we turn off the gas that will be facilitated by moving to an electric water heater, likely a Marathon by Rheem. We had one of these in a past house and it seemed to work fine and be as efficient as an electric tank water heater could be.
The water heater won't get replaced for another month or two so I'll still be researching the HPWH's to see if I can be convinced of their efficiency and durability. The installation of said water heater will be in the garage where the current unit is. I've gotten mixed messages about HPWH garage installations so any input there would be appreciated as well.
I do want to note that in general the replacement of the water heater is in no way related to the HVAC system. They are just both original to the house (1991) old, worn out, and I happen to have the budget to do both at the time.
Thank you all for the input.
Andrew