Feedback for new construction HVAC proposal

pds22April 24, 2013

Building new home in SE Michigan. Approximately 4,200 sq feet 2 story house with 2,100 sq ft unfinished basement.

Builder and HVAC subcontractor proposing following based upon Manual J calcs. Would appreciate feedback, suggestions concerning HVAC equipment being proposed.

Manual J calc output
Zone 1 - 1st floor and basement
Total heat loss = 73,278 BTU
Total heat gain = 34,705 BTU

Zone 2 - 2nd floor
Total heat loss = 59,754 BTU
Total heat gain = 32,475 BTU

Zone 1 & 2 specification
Input heating = 80,000 BTU
Output heating = 78,000 BTU
Blower motor HP = 3/4
Coil & condenser 3.5 ton capacity 42 MBH
Air volume = 1,400 CFM

HVAC equipment proposed for both Zone 1 & 2
Furnace - Luxaire LP9C080C16MP12C
AC - Luxaire TCJF42S41S3 14.5 SEER
UV light - Field Controls UV-16/120
Air filter - Generalaire MAC2000
Humidifier - Generalaire 900A
Thermostat - Honeywell Focus Pro TH6320WF1005/U

- Any concerns, missing information as to specs and HVAC equipment being provided? I did not receive actual Manual J raw #s input / used but final output #s from the HVAC engineer that was consulted.

- For the Luxaire AC, should I be asking for Acclimate series AL6B 16 SEER rather than LX series TCJF 14.5 SEER? Understand additional cost with increased SEER rating, my concern is whether there are greater mechanical improvements, features, e.g compressor, fan design, etc. that should be considered with Acclimate series

- For UV light, I would've assumed Luxaire being proposed rather than Field Controls. Should I have any concerns about this? Also recommended to have 2 UV lights rather than 1 UV light per furnace?

- Thermostat wise should I be asking for Honeywell Prestige thermostat instead of Focus Pro? Or request Luxaire Acclimate thermostat instead?

Appreciate help and thanks in advance.

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I assume that your new home will have both superior building and insulation qualities.

Is basement below or even partially below grade?

I find the load calcs questionable particularly for heating. I suggest they be reviewed and retaken by a different person. Do you have these load calcs in writing, broken out for each zone, on the software letterhead?

Why a 3.5 ton AC condenser when load calc indicates a three ton?

If you expect good comfort and plan to use the basement regularly for living area, I would want a zoning control for that system. Well worth it.

Luxaire is sister company to York. Furnace appears to be top of line modulating model. I would want the Acclimate communicating control for best operation and full functionality.

Where will furnaces be located? If the furnace for second floor is to be located in attic, how will attic be insulated?


    Bookmark   April 24, 2013 at 6:24AM
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Thanks tigerdunes for reply and feedback.

Yes basement is mostly below grade, there's a french door walk out in the rear. Do have plans to finish and use the basement in the future. Builder mentioned using dampers for basement but should I request a specific controled zone instead?

Have load calcs in writing by zone but not on software letterhead. Will inquire to that. I assumed would've been a print out of some sort rather than sheet hand input. But don't know what's to be expected, typical practice with the load calcs.

Is there something particular with heating calcs that I should dig into with the builder?

Furnaces will both be in the basement. Builder was not keen on putting 2nd floor furnace in a separate mechanical room on the 2nd floor. Mentioned that would need to insulate duct work in attic

    Bookmark   April 24, 2013 at 8:45AM
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I also question the load calculations. I assume the first and second floors are each 2100 sq. ft. If that is the case, then how can the heat gain of the second floor be less than the first floor?

How much insulation will there be in the attic and exterior walls? What are the typical winter low and summer high temperatures?

    Bookmark   April 24, 2013 at 8:49AM
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Yes, install a separate zoning control for the basement. Now is the time.

Yes, I think both furnaces are oversized. Makes me wonder if he sized the furnaces not for the heating BTU capacity but for the 4 ton rated blower that would be needed for the 3 1/2 ton condenser.

Yes, based on heat gain calc, a three ton condenser seems to be right size, not 3 1/2 ton as quoted. This should be questioned. Keep in mind, 36 KBTUs=3 tons.

I would want to know the design temperatures used both inside temp and outside temp both for winter heating and summer cooling.

You want excellent ductwork insulation for attic. That's a long way to blow air. You might consider an 80% furnace for second floor installed in attic. This would eliminate the long distance or perhaps insulate attic where it can take a high efficient condensing furnace without fear of freeze ups. The 80% would be a less expensive option. Discuss the options with dealer/GC.

Nothing is easy is it?


    Bookmark   April 24, 2013 at 9:03AM
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Yes 1st floor is 2200 sq feet, 2nd floor 2000 sq ft.

All brick exterior. Insulation to be cellulose in house and garage (R-19) and attic (R-49). Closed cell foam on basement walls. Also 1" closed cell foam on exterior walls. Foam windows, caulk wall plates and in-between framing members.

The typical winter low temperature is low 20's with typical summer high temperature in the mid-80s'. Get a few cold weeks where in the teens and opposite in the summer where it does get 90+ for a few weeks at a time.

    Bookmark   April 24, 2013 at 9:03AM
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Yes did discuss with builder as to HVAC unit to be located in 2nd floor in separate mechanical room. Builder disagreed as required duct work to be insulated, heat loss in attic given winter cold temps we have in MI. I did not object as accustomed to seeing homes with HVAC units in the basement and did not read anything online where 2nd floor HVAC unit is a must.

Will inquire as to inside and outside temps used.

    Bookmark   April 24, 2013 at 9:10AM
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Based on your insulation values and the typical winter and summer temperatures, I feel the load calculations are not accurate. You need to dig into the details of how these numbers were calculated.

I agree with your builder about putting both furnaces in the basement. I have the same set up in my house so I know from experience the set up works and in my opinion it is more energy efficient than having a furnace and duct work in the attic. The key is to have adequately sized duct work running from the basement to the farthest room on the second floor. This should not be a problem with the size of your house.

    Bookmark   April 24, 2013 at 9:21AM
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