Comparing two HVAC bids - would love your input

dreamhome2013November 14, 2013

Hi - normally I post in the "building a home" forum, but I think it's more appropriate to post this here.

We are building a new house, 3700 sq ft, two story, in Austin TX hot climate. Plus separate guesthouse/casita but it will just have an electric heat/cool unit. I have two HVAC bids for the new construction.

I've pasted them each below. My questions are:
1. they both recommend heat pumps for heating and cooling. I've done some research on them, but no real experience. Is that sufficient for TX summers?
2. it's hard to compare apples to apples with the bids. Is there anything that one is including that the other isn't?
3. is there anything missing that you would expect to see in an HVAC bid?
4. The casita won't have ductwork, but how would the exhaust fan work in the bathroom? One bid mentions the casita, but not sure what they're saying.

Bid A is attached here. I'll attach Bid B as a follow-up.

Thanks in advance!

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dreamhome2013

Total of bid A was $22,994. Bid B is $26,400.

Here is Bid B:

    Bookmark   November 14, 2013 at 9:49AM
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jackfre

I would suggest you go Fujitsu for your Mshp. They have 12's that are 26 seer and would be the same price. I'm putting one in this weekend;)

Regardless of whom you choose, I would want a bid with model numbers of equipment. Not saying your contractor would stiff you, but it has happened. Also, I would install a clause that calls for a pressure test on the duct system and I would have a third party do it. Google "doeduct leakage" to see what I am talking about. I'd also look at putting mshp on the second floor. That eliminates all the attic ductwork and would be more efficient. They are great in bedrooms and really quiet. They give better zone control too.

    Bookmark   November 14, 2013 at 10:39AM
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mike_home

The first thing I urge you to do is to find a HVAC contractor who will do a heating and cooling load calculation. This is known as a Manual J calculation in the HVAC industry. You can see you have two bids which are proposing different sizes. These contractors are using rules of them which often lead to over sized equipment.

These bids look unprofessional to me in my opinion. Keep looking for a better contractor.

Your quotes must have all the model numbers the heat pumps, air handlers, coils, and any other equipment you buy. If you don't get this then you don't have a valid quote.

A bathroom ceiling exhaust fan can be connected through a flexible duct and exhaust to a vent through the roof. The duct should be insulated in order to prevent condensation. This has nothing to do with the HVAC duct work.

    Bookmark   November 14, 2013 at 1:04PM
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dreamhome2013

Thank you both for the excellent info. Had no idea about manual J calculation, but have started to do some research on it and will ask the contractors to provide it. will also ask both bidders to provide more details in their bid. One of them (the one who has the more details) comes very highly recommended from a few people we know so I'm not giving up on him just yet.

Good luck jackfre with your MSHP install. :)

    Bookmark   November 15, 2013 at 3:04PM
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jackfre

Keep in mind that the Manual J has an 18% duct leakage factored into it. That should be considered when choosing your mshp's.

    Bookmark   November 16, 2013 at 11:02AM
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energy_rater_la

duct leakage can be mininized if all ducts, plenums, supply boxes & return air are mastic sealed.
not duct tape, not foil tape.
paint on mastic applied nickel thick or
mastic tape like Hardcast brand 1402 mastic tape.

x2 mike's post.

also, 13 SEER a/c just meets the legal mininum allowed
by law (code) 15-17 SEER heat pumps will provide a
better savings & quickly re-coup the extra costs.
variable speed air handlers will help to handle summertime
relative humidity.

get the load calc based on your plans, specific insulation
values & types, orientation, window shgc & ufactors.

building a home this size invest in an independent load calculation (manual J) duct sizing & design.
then shop the load calc you own to hvac companies.
have enteries in load calc based on design temps
for your area & reflect the specifics of your build.
hvac should be sized for average temps and not the
5 days per year of extreme temps. this is why
there are specific design temps to be used.

otherwise the hvac companies will run a quick load
not release it to you until you sign a contract
and you get what they decide to make the load calc
verify. it is common practice to not release load calc
as homeowner can use the company that did the
calc's to shop job to other companies.

foam insulating the roofline will put ducts in semi conditioned space & save you about 20-30% in
energy costs. upgrading to foam will also reduce
tons of hvac required.
take it a step further & use foam sheathing on exterior
walls, tape the seams & caulk it air tight.
a tight home is an efficient home.

bid one mentions fresh air intake. this MAY be necessary
but should be planned for & designed. damper is set
to cubic feet per minute (cfm) of air required by ASHRAE
62.2 ventilation strategy, not just a random amount.

blower door testing of house, duct testing of ducts
should also be done.

oversized hvac systems cost more upfront to purchase,
more to operate, contribute to high RH in the home.
sizing the systems is the best investment that you
can make now for comfort and affordability.

think about hiring an efficiency expert.
resnet.us is a good place to start.

best of luck.

    Bookmark   November 16, 2013 at 11:51AM
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peeler

7 years ago, I had a house built with 3 HVAC units. My bids for installation were much like yours (i.e. minimal detail, no load calculation, etc.). As an uninformed consumer, I chose what I thought was the best bid and ending up getting CRAP. The installer I chose was worthless, and I am redoing his work as my budget allows. Among other problems, he used flex duct all over the place which is crimped in many locations, and he used regular duct tape for most of the connections. His choice of air paths was illogical. My point is that there is so much that goes into installing a heating and air system in a house that you would be wise to educate yourself and be an informed consumer. The installer is as important as the components. You have received good advice from others on this thread regarding load calculations. My suspicion is that your first 2 bids are not from contractors that you want to use since they didn't really tell you what you should be asking. Your contractor should educate you why his bid is the price that it is. He should teach you why he is the one to do the job. You should go and see some of his work. Also know that if you are building a "forever house" and really want an ultimate quality job, you might consider all rigid ductwork--no flex.

P.S. Bathroom fans are very diverse. You have many levels of quality and noise level from which to choose. You will need to specify what you want. Do not allow the contractor to choose that for you. You may want to research the Panasonic whisper quiet bathroom fans. Those are pretty nice.

    Bookmark   November 18, 2013 at 7:47AM
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tigerdunes

Agree with Mike.

7 tons for 3900 sq ft?

Nothing wrong with R8 flex for supply runs. I would want galv metal for trunk lines both supply and return.

To be clear, home will be all electric or do you have nat gas service?

Since this is new construction, I would expect quote to have more detail. I want to know model number of air handlers. Any filter cabinets? Should be one for each system. How many supplies/how many returns and where will they be located?

IMO

    Bookmark   November 18, 2013 at 10:10AM
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udarrell

Here is a free online load-calc; do the areas separately.

If you know & do the inputs right it will get the loads fairly close. Do not oversize equipment.

Here is a link that might be useful: free online whole house load-calc

    Bookmark   November 18, 2013 at 6:20PM
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