hvac crawl vs attic location

14 years ago

My 1400sf ranch is located in the midwest. To enlarge half bath to full, the mechanics closet is key. The natural gas hvac and natural gas water heater need to be relocated outside the conditioned space. Interior relocation is not an option...NO available space

For six months we've interviewed five hvac and plumbing contractors. The contractor with creative solutions, best equipment (Lennox, we had before), and most interest (estimator brought production manager and hvac engineer on second visit), presented two options.

#1) crawl space (3.5' dry w/pastic & gravel)

#2) attic space (10' pitch with attic fan)

Please let me know the challenges of both options and which option you would recommend.

Thank you,

dormandj

PS The hvac package unit was too expensive.

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Comments (10)

baldloonie
14 years ago
Crawl! They don't get to 120Â°+ in the summer!
creek_side
14 years ago
For maximum damage potential, and in order to punish your HVAC techs and installers as harshly as possible, the attic is a safe bet.
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Regarding ductwork, do you know how many return air ducts you have? Since often times ductwork systems are undersized to begin with, I don't like the idea of increasing tonnage without ensuring the ductwork is in good condition and properly sized. However if the old system did a good job handling the the temperature throughout the house, it may be okay. An extra return may need to be added. The XP16 is a heat pump. I assume he meant XC16. The XC16 is a 2-stage unit, which can help control humidity better, but I would not use it without a furnace with a variable speed blower. It is the variable speed blower that is required to get more than 14 SEER in most cases. The XC15 is advertised as a very quiet unit, but that doesn't mean the XC16 will be loud (the brochures should have the dBa sound ratings). The Lennox guy should have given you model numbers. You'll want to talk to the Trane dealer about sizing to ensure 2.5 tons is sufficient. Did any of them do a load calculation to prove that you needed more capacity? You aren't comparing apples to apples with both quotes, since the Lennox furnace does not have a variable speed blower, which I'd recommend for greater efficiency and comfort. They can also overcome slightly deficient ductwork systems by adjusting their speed. If the ductwork is in very poor condition, however, they can be louder (I think you'd know if the ductwork was in poor condition/undersized, as you would have had symptoms with the old system, like uneven temperatures, noise, and lack of airflow).
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Thank you for the comments and apologies for the confusion. I am probably not using the terminology "split zone" and "2 zone" correctly. I will be moving the furnace and coil from a first floor HVAC closet to the attic and the condenser from the ground to the roof. I was also told I need all new ducting (current ducting and HVAC are from mid-1980s). I have received two very different quotes for equipment. Please see below. Quote 1: 4 ton 18 Seer Horizontal Split System, Furnace Model: 58CVX090116 – 80% (2 Stage Heating – Variable Speed), Horizontal Coil Model: C48H175P156, Condenser Model: 25VNA949A003 – (5 Stage Cooling – Variable Speed). Carrier 2 Zone Infinity System- Zone 1 for first floor, Zone 2 for second floor. Infinity user interface and smart sensors Quote 2: Bryant 4 ton 14 SEER Horizontal Split system. Install Bryant 4 ton 80% Single Stage furnace model# 310JAV048090. Install Bryant 4 ton 14 SEER R410A coil model#PL48H210P75635. Install Bryant 4 ton 14 SEER R410A condenser model# 105ANA048000. Quote 1 is significantly more expensive but has far better equipment than Quote 2 and has 2 zones. I have asked Contractor 2 to quote me a more efficient condenser (because it will be on the roof and I want it to be quiet) and a 2 zone system. He is in the process of doing so but said for the size of my home, it will take many years of electricity cost savings to break even on the additional cost of installing a 2 zone system. One other thing to note is that there are 2 bedrooms on the first floor and one of my children will be sleeping on the first floor so we will likely need to cool both floors at night anyway. Hope this helps clear up any confusion!
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I have to agree - wow that is high cost. Not that there is much you can do about that. Nearly identical set up here is $18k. Have you asked about another HVAC installer? Who designed the rooms? If the builder did, it would seem it is up to him to come up with a solution. Is there not an option to change the equipment to fit in the smaller space? I don't know but would a lower efficiency option be smaller? I built on the coast in NC and my utility closet upstairs is pretty small - 3x3 I think - and it houses a Seer 15 heatpump - 2 tons - just fine. Mounted vertically with ducts between levels. Are you crystal clear on the flood zone issues? We are in a VE zone and have the lower unit hung under the house. We are on pilings that we park amongst. In the area without parking, the ceiling drops and that is our lower unit. We are comfortably above BFE. In our neck of the woods, if you could do crawl, you could have units there. 56 feet is nothing. Ideally units are centrally placed of course but one current in construction house has the downstairs unit not central and goes over 56 feet. Does it financially make sense to do heatpump and then solar if it fits in your closet? I totally get that heatpump is a hard sell with your high electric rates but if paired with solar, it might make financial sense. So while you pay $20k extra for solar, you save $2000 a year and then can fit a heatpump in a closet. Just guessing. Wonder if you could do a mini at the far end of the house?
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sean_m
14 years ago
Neither if you care about efficiency and longevity. It belongs in the conditioned space.

I'm surprised that the package unit was more expensive. They're traditionally LESS expensive than split systems. I'd seek other bids.

I'd also consider mini-split systems. They make concealed air handlers which can be fit just about anywhere, like in/above closets, etc.

Is there a garage or similarly-attached space you can put it in? Something's better than nothing.

If all else fails, I'd have to say crawlspace, but be careful. Crawlspaces are notorious for all sorts of critters (that like to eat everything except metal ductwork), mold, mildew, and water.
dormandj
Original Author
14 years ago
Thank you for the advice. The verdict was tied. We went with the crawl installation. They should finish today. We are excited about joining the 21st century with a full master bath.
dormandj
Original Author
13 years ago
We have a new Lennox high efficiency system--replaced in Nov 2009 for 1400SF ranch in midwest. The furnace was great, but the 2TON AC is struggling to get to 76 when thermostat is set to 74 degrees (we have an attic exhaust fan too!) HVAC company has double-checked and fine-tuned everything. Lennox ACs only come in whole number tonnage, but the company says to upsize to 3T would cause reworking ductwork. They have offered to put in 12" attic insulation, first. What is your advice?
weedmeister
13 years ago
Go with the insulation and see if that helps. Also, check your windows.

And don't forget the tax credit.
creek_side
13 years ago
Get rid of the attic fan. They depressurize the attic and suck your conditioned air right out of your house. Been there, done that.

The insulation won't hurt a bit, but before having it installed, seal every penetration into the attic that you can find (wires, pipes, whatever) with caulk or foam. Also seal any ceiling openings, including can lights, and around the edges of ducts. Remove the registers to see if there are gaps between the duct and the drywall. Seal any you find. Don't forget vent fan openings in the kitchen and bath.

Check vent fans to make sure the dampers are closing properly, too.

Make sure the attic is properly vented without the fan before you install any insulation. And don't let the insulators block any soffit vents when they insulate.
dormandj
Original Author
13 years ago
Weedmeister, thank you for the tax advice. I thought since we took $1500 in 2009 for the furnace that we had maxed out. But insulation qualifies for another tax credit!

Creek side, great multiple sealing tips...thank you! Just want to be sure I understand your advice on the attic fan. It's not a full house attic fan located in the attic. Rather it's an attic exhaust fan that removes only attic heat. Your thoughts?
david_cary
13 years ago
Creekside knew what you meant. Attic exhaust fans are one of the worst ideas going. They seem to make sense and in the right setting might help. But the reality is that most cause more harm than help. As you pull heat out of the attic, you depressurize it. That causes increased leakage out an average ceiling.

I wonder if you sealed the ceiling really well, it an attic vent wouldn't be bad. I mean people like to talk about vent closing being very wasteful as the increased pressure causes increased leakage in the ductwork. Well this is all based on a study of fairly old houses. Take a well sealed duct system with fresh mastic everywhere and the downside of closed vents is reduced significantly.

But as a rule of thumb, the average attic fan is a great big waste of energy. It does make you attic more comfortable though....
dormandj
Original Author
13 years ago
David, Thank you. This is good to know. dormandj

hvac crawl vs attic location

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