Seeking help on HVAC/insulation investment choices

10 years ago

Hi all, I wanted to request advice on making a decision on our home HVAC system and insulation needs. Sorry in advance for the very long post.

Situation:
We (me, wife, 2 kids 2 3/4 and 4 months) live in a ~3300 sq ft 2 story home (pull-down attic and no basement) in central VA, built 1994. We bought the home 2 years ago. We have a 2-zone system, with a 10 SEER Aquatherm gas furnace located in the garage, providing heat and cooling for downstairs (Goodman unit outside the house), installed ~2007. For upstairs, we have a Payne heat pump (2004, 10 SEER) also outside, with a 2 ton air handler located in the attic. Our thermostats are non-programmable. The ducts are ductboard for the main line, with flex going to the vents. There are two returns downstairs, and one upstairs. The insulation in the attic is blown-in cellulose, and ~4-7" deep depending on the location, so I guess ~R20 or so. Our total utility bills are ~$3000-3500 for the year (gas and electric), though I don't know how much is due to heating and cooling. Since I'm a stickler for costs, I prefer not to turn the thermostat too high in the winter (max 71) or too low in the summer (min 74-76), but the result is that it's never quite comfortable, and there is wide variance in comfort levels in some rooms. I am now on a mission to improve the insulation and comfort in our house, and hope to do it in a cost-effective manner.

Actions: I've done some small things (self-caulked some holes in the upstairs ceiling, weather-strip the windows, bought electric auto-off space heaters for the colder rooms), but the reality is those are somewhat marginal relative to the bigger issues. I had an HVAC expect come in an do a blower door test (infiltrometer), and the software found ~35% duct leakage upstairs, and ~20% duct leakage downstairs. He also did a Manual J calculation and found that upstairs needed a 3 ton system (he recommended SEER from 13 to 15.8, depending on what I was willing to spend), 2 new returns (located in the guest room and the master bedroom, both of which are cold in winter and hot in summer when the rest of the house is comfy), some additional vents and some enlarged vents. He said we didn't have to replace the ductboard main lines in the attic, but he did add that it's an inferior product and they've never installed it in 46 years in business. My commercial architect father-in-law recently visited, and said that the upstairs duct design was garbage and should probably be replaced.

We are definitely going to seal the downstairs ducts. For upstairs, I'm wondering whether to just seal the ducts and wait for the heat pump to die, or whether to seal them and get a new heat pump, or to replace the ductwork and get a new heat pump. We can afford all situations, but I'd like to do it smartly.

I did have some others come in to check out the situation, but none did the blower test or Manual J calcs, or even offered it. Plus this guy's price happened to be better as well than competing quotes.

Option 1: Seal the downstairs ducts and the upstairs ducts. Nothing else. Cost ~$2000 (I'd also separately get programmable thermostats for upstairs and downstairs)
Option 2: Seal the downstairs ducts, seal the upstairs ducts, add the recommended returns and vents, replace heat pump with new 15.8 SEER, 3 ton heat pump which includes variable speed motor and programmable thermostat. Costs: $10,200
Option 3: Seal the downstairs ducts, completely replace the upstairs ductboard with metal ducts and insulation, adopt new ductwork design including new returns and vents, replace heat pump with new 15.8 SEER, 3 ton heat pump which includes variable speed motor and programmable thermostat. Costs: $11,600 (basically $1400 more than option 2).

We've been in the house 2 years, and while I can't predict the future, we have no plans or energy to leave the house. I'd say we'd be here at minimum 5-7 years barring unforeseen circumstances, likely more.

Suggestions? Is it worth getting the new heat pump system? Is it worth replacing the ductwork in the attic (metal ducts instead of 20 year old ductboard)? Any recommendations would be greatly appreciated

Thanks!

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Comments (4)

trihiker
Original Author
10 years ago
last modified: 9 years ago
I should have added that the recommended systems were Lennox XP17-036 (17 SEER that comes down to 15.8 SEER for reasons that I forgot), and XP14-036 for 15 SEER, both with 10kw heat strip. The XP17 also comes with an air cleaner and a fancy iComfort thermostat (that I don't truly need).
mike_home
10 years ago
last modified: 9 years ago
You have a two HVAC systems for your two story house which is relatively young. You should not be experiencing rooms which are too hot or too cold. I suspect you have significant duct supply problems. The supplies in the attic likely should be done with a combination of a hard main supply and R8 flexible ducts. The downstairs ducts should be sealed wherever it is practical.

You should make adding more insulation to your attic the first order of business. If you are handy you can do this yourself. You want an minimum of R30. More is better. You also should seal the attic hatch. You can buy a cover or make one yourself. It is not hard.

I am a little suspect of the Manual J calculation. A 3300 sq. foot house built in 1994 should not require 6 tons of cooling. Do you have a copy of the calculation report? Did the contractor explain it to you?

I would not replace the gas furnace with a heat pump. What are your gas and electric rates? Is the garage heated? If it is, my vote would be to install a 95%+ efficiency furnace when you are ready for replacement.
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I'm disappointed that what had at first seemed a very balanced comment was followed by what seems to be misinformation and misdirection. People buy ground source heat pump equipment because they want to and can afford it. Or decide they need to in their locations. They're hugely more expensive than alternatives, which is why they're still not very common. "When’s the payback on a Tesla? People still choose to buy them for reasons other than the ‘bottom line’." Not a comparable. A false analogy. "I would not choose natural gas or propane for reasons relating to the environment, safety, IAQ & paying for yet another utility hookup for an energy source that might not even be used for months on end during the year." What effect having a gas furnace has on indoor air quality. Another hookup? Most people prefer gas cooking appliances and besides, the OP is talking about an existing home, he either has gas service or he doesn't. "Rather than spending perhaps tens of thousands of dollars on a Solar Array, I would sooner invest that same money, hopefully less, in a ground loop for a Geothermal system." Sure you would, that's the business you're in. The ground source heat pump market is not growing as expected by those in the industry, which suggests that your opinion isn't widely held or easily sellable. In many parts of the country, solar panels can have a quick payback. Not so ground source heat pumps. "I often hear about Solar Panels when geothermal is mentioned, as an alternative way to save money by creating energy." In a place like Texas, where electricity is cheap (other than during cold weather crises as they just experienced) there's likely no payback from a solar panel installation. People do it as a personal statement, call it for environmental or other personal reasons. Like buying the Tesla, not a financial decision. An HVAC system blows warm air when it's cold, cool air when it's hot. It's one of those things people don't care about - either it works or it doesn't work. Spending extra money for an exotic system doesn't equate to extra payback when the home is sold. Neither owners, nor visitors, nor people passing by, nor anyone else, concern themselves with what's doing the work. It's equipment that doesn't produce an experience for someone in the house if it's working. In the US, there are vast areas where electricity is cheap. It will remain so for some time. People don't spend money today to potentially save money 10 years out when market conditions may or may be different. I suspect you could build a house with mahogany or teak framing. Or you could paint the framing bright colors. Why bother, you can spend less money and effort and get something else that will do the same job. "We almost never use setbacks at our home - even when going on vacation for weeks on end with no one home, our geothermal just runs." You're combining two different things to produce confusion. Thermostats that have a setback feature ALL are set up to provide lower overnight temperatures to have more comfortable sleeping conditions and then a recovery in the morning before wakeup time. As sleep specialists recommend. That in demand comfort features isn't possible with ground source heat pumps because the warm up period from a setback is too slow to be convenient to use, absent triggering a secondary heating source (like a furnace) to help. THAT'S why you don't "believe" in setbacks with a heat pump - they don't work. Turning down a thermostat during heating season when the home will be unoccupied is not a "setback" as that word is most commonly used. It's done to save money, why heat a vacant house? No setback thermostat is needed, even a dumb 50 year old analog thermostat can be turned down.
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energy_rater_la
10 years ago
last modified: 9 years ago
I'd invest in the duct sealing (including returns) of both systems. see what that does as for comfort &
air flow. this is one investment that quickly
pays for itself. paint on mastics or true mastic tapes
are the only sealants I'd allow.

there is nothing wrong with ductboard & it is not
an inferior product. a well installed, correctly
designed & sized duct board plenum will
perform just as well as a sheet metal plenum.
I have to admit...statements like 'inferior product'
send up a red flag for me.
IMO it is a short way to say.."I'll charge/make
more to tear it out & replace it"
that he wants to increase size of the upstairs
system is the second red flag.
bigger isn't better.

take a look at it yourself. is the ductboard plenum
larger in size at the equipment & reduced down
towards the end of the plenum? is it in good shape?
are the flex runs straight? are the ducts well sealed
at the plenum? take a couple of pics & post.
we can't see as well as you can...but we will look.

now if there are comfort issues & obvious problems
with the supply plenum & ducts...then you'd have reason
to think about re-design. but often comfort issues
are solved by installing manual dampers so that you
can adjust air flow and by increasing size of a duct
or two. crimped or compressed ducts reduce air flow..
but are usually easily fixed or replaced.

30% duct leakage isn't uncommon at all. it is more
the norm than the exception.

so if you invest 2K in duct sealing & then still feel
the need to replace equipment..
but I'd like to see pics before going further.

before adding insulation, complete all work in attic
including duct change outs. sealing or modifications.
any equipement change outs should be completed.
then..and only then..does insulation install need to
be consitered.
adding insulation prior to any work will make it
more difficult to work, insulation will be compressed
as work is done, and any insulation moved to access
work may not be properly replaced.

before insulation though...air seal. supply grills inside
the house and bath vent fans cover oversized cuts
in ceilings. recessed lights that aren't air tight allow
leakage from attic into house.
accesses into attic will also leak, and should be
built up around access to hold insulation in place
as access is opened.

blower door test should have provided list of
areas of infiltration. what were the blower door
numbers (example 5000 cfm @ 50 pa)??
was duct leakage test done at same time?
what plan of action/information/advice did auditor
give you @ time of audit?

I'd suspect that load calc wasn't done and equipment
is oversized.

in my area we ususally put gas heat on first floor
and heat pump on second floor. heat will rise
in winter to suppliment heat pump heat on second
floor.

do you have a prefrence as to gas or heat pump?
is one cheaper/higher than the other to make
choice for you?

I'm glad to see that you are willing to invest some
time in determining what is best for your house.
rather than just throwing $$ at newer bigger
equipment it makes sense to evaluate what you
have. take time to make decisions that will
provide comfort and savings.

best of luck.
energy_rater_la
10 years ago
last modified: 9 years ago
My mistake...the hvac company did the blower door test...
this company is the one who said ductboard was inferior,
wants to upsize second floor unit...and tested ducts.

since you are needing advice on what investments
to incorperate in your home...what about an
independent doing the testing, making
recommendations & verifying everyone's work?

the best gain for you is someone not selling you
products, that installs are verified & tested,
and that he/she can offer unbiased information,
that is specific to you & your house.

energy raters test both house for leakage,
blower door test and ducts for leakage with
a duct blaster.
most can pinpoint leaks of both house & ducts.
you get recommendations of how to seal &
verify that work has been done correctly with
final inspection & testing.

resnet.us is the main source for energy raters.
duct testing is part of each rating.
this will let you know where you are now..give
you recommendations & paybacks of upgrades &
verify on end of job.

bpi has energy auditors, not sure if they
do duct testing as part of audit, or if they
re-test to verify what was actually achieved.

just something to think about.
advice on a local level from someone with no
dog in the fight. an independent unbiased third
party hired by you.
you are getting ready to spend a good amount
of cash...do so wisely.

best of luck.

Seeking help on HVAC/insulation investment choices

Comments (4)

trihiker
Original Author

mike_home

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Seeking help on HVAC/insulation investment choices

Comments (4)

trihikerOriginal Author

mike_home

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trihiker
Original Author