Author Topic: Seeking help on HVAC/insulation investment choices  (Read 2965 times)

trihiker

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Seeking help on HVAC/insulation investment choices
« on: November 19, 2013, 11:31:31 AM »
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 HVAC 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 expert 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?  Any recommendations would be greatly appreciated

Thanks!

hoodedfalcon

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Re: Seeking help on HVAC/insulation investment choices
« Reply #1 on: November 19, 2013, 12:03:31 PM »
I've recently been through an HVAC/duct work ordeal, so I just wanted to chime in with my experiences and some information.

I had a 13 year old 10 SEER gas pack that bit the dust after years of heating and cooling very inefficiently (and sometimes not at all!). I had an energy audit done around the same time. I was told my duct work was crap, and thanks to a possum family moving in under the house last winter, sorta shredded.

So, here goes:
1. You can seal the ducts yourself using mastic. MUCH cheaper than paying someone to do it. Not sure if this is something you'd be willing to take on yourself, but it's something to consider. Check the internets.
2. Is 71 degrees a typo for heating in the winter? Because I would consider heating to 71 pretty extreme.
3. After replacing my HVAC, my electric bills decreased significantly. Like, 30-40% during the summer (I also stopped using my clothes dryer). I haven't been through a winter yet, but I expect most of the savings will be summer savings because of a better SEER unit (I went with 15 SEER).
4. Tax credits that expire this year: http://www.energystar.gov/index.cfm?c=tax_credits.tx_index
5. My local utility company also offered a rebate - I would check to see if yours does.

Personally, I would probably hold of replacing any unit unless it died or would cost over 1K to fix. You could go ahead and install a programmable thermostat yourself. That could make a huge difference.

Spork

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Re: Seeking help on HVAC/insulation investment choices
« Reply #2 on: November 19, 2013, 12:09:40 PM »
I'm by no means (NO MEANS) an AC expert... but I talked to a guy that designs AC compressors for a major name brand you've heard of when I built my house.

To paraphrase what this guy said: 
* 13 seer is a government minimum.  They'll never suggest you put in less because they can't.
* he suggested a 13 seer with a variable speed indoor unit.  He said this effectively makes it a 14 seer.
* he said as you go up in seer, you go up in price and from 13-15 it is about "even money".  I.e: if you spend it on the unit, you get it back on electricity bills.  Over 15 he said "was a waste of money".  (I am sure with time and better engineering, those words will be false... it was just what he said at the time).
* he said for AC units: all the major players were fairly equal in quality

Did the guy also test how air tight the house was?  Or just the ducts?  Depending on your attic design...  is there any way to do spray foam insulation?   One advantage there is that it is generally done at the roof level -- making your duct runs inside of the insulated envelope.  You'd still care some about the HVAC leaks, but not nearly as much.

BoulderTC

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Re: Seeking help on HVAC/insulation investment choices
« Reply #3 on: November 19, 2013, 03:46:21 PM »
2. Is 71 degrees a typo for heating in the winter? Because I would consider heating to 71 pretty extreme.

I agree. We have an upper bound of 62. Granted, we don't have kids.

Also - I work in the energy efficiency field and specialize in residential HVAC systems. Without seeing more specs, its hard to prescribe, but in general, duct sealing saves about 25% of your heating and cooling energy. That's a lot! You definitely want to get your house nice and tight before you replace equipment. As far as the HVAC systems, once you have your system sealed, I'd recommend replacing them with something more efficient (above SEER 13). Here's a nerdy document that you can use to calculate energy savings from different energy efficiency measures. Note that equivalent full load hours (EFLH) are highly debatable and dependent on many factors, so don't put too much trust in these estimates.

http://www.neep.org/Assets/uploads/files/emv/emv-products/A5_Mid_Atlantic_TRM_V2_FINAL.pdf

And definitely check if your utility offers rebates. All utilities are required by law to save a certain amount of energy per year, and devote a big chunk of their budget to making that happen. My job is to evaluate whether the energy savings claimed by utilities are realized.

trihiker

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Re: Seeking help on HVAC/insulation investment choices
« Reply #4 on: November 19, 2013, 06:02:19 PM »
(OP here) Thanks everyone for your quick replies!  In response to some of the questions:
- I thought of sealing the ducts myself, but I really wouldn't know what I'm doing.  I'm not exactly a handyman.
- 71 degrees isn't a typo. I'd prefer to keep it on 69, but my wife wants it warmer.  Even at 70 or 71, it isn't exactly T-shirt comfort in the house, it's still sweater and jeans comfort.  At 65 it's quite cold in the house. (the blower door test which showed 20-35% duct leakage might explain some of that).
- I'm aware of the federal and state taxes, and the rebates offered by my local utility - thanks for that.
- the guy did test how airtight the house was.  I had 59 square inches of leakage above the "optimum leakage", of which 51 sq in. was coming from the ducts.
- i did not ask about spray foam insulation on the roof, but he did quote ~$2k for additional blown-on cellulose insulation in the attic to get it up to R50

Our heat pump is 9 years old and works, but not great.  I'm sure I need to seal the ducts, but am wondering if it's worth replacing the ductwork altogether with new metal ducts instead of the ductboard (extra costs of $1400).  I'm also wondering whether to actually replace the heat pump, though I'm leaning toward upgrading it rather than letting it limp along another year or three.

BoulderTC

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Re: Seeking help on HVAC/insulation investment choices
« Reply #5 on: November 20, 2013, 01:27:10 PM »
I'm sure I need to seal the ducts, but am wondering if it's worth replacing the ductwork altogether with new metal ducts instead of the ductboard (extra costs of $1400).

I think that the material of the ducts doesn't matter as much as if they are sealed. I think your money would be better spent on a more efficient unit rather than upgrading to new ducts (which would probably also need to be sealed). Is there something about ductboard which won't allow you to get as much of a seal? Even so, I don't think it's worth $1400.

Another added bonus is that duct sealing decreases the work your blower fan has to do, thus decreasing the maintenance needed on your unit, and might extend its life a little longer.