Adding A/C and HP to 80 year old home! Big difference in quotes!

12 years ago

Hey guys! We're renovating and adding onto an 80-year old home in south Texas. We have to add A/C and heat, completely rewire the entire home, add a kitchen, add a master suite, reroof...the list goes on and on. It is two story, rock and stucco, about 2800 sq ft (after addition), pier and beam foundation, and will have half new windows/half old windows. I have several bids for installing A/C and heat pumps and would love some input from you guys! I don't have any specific info on one of the bids (but will get it), but here's what I have on the other two:

Bid A ($19,863):

Two High Efficiency Trane (XR 13 Series) Heat Pump Systems with high efficiency (Hyperion) air handlers and auxiliary strip heat

(1) 3.5 Ton system (1st floor) 41,500 BTUH 14.00 SEER

(1) 3.0 Ton system (2nd floor) 35,400 BTUH 14.50 Seer

Air distribution (1st floor)-exterior wrapped sheet metal ductwork (R-8)

Air distribution (2nd floor)-fiberglass trunk line wtih flexible duct run outs (R-8)

Dampered collars for each flexible duct run out for air balancing

Sealing all start collars to fiberglass trunk line wtih mastic.

Low voltage conduit

Hart & Cooley aluminum curved blade supply grilles and fixed bar retrun air registers

Trane 7-day programmable digital touch screen thermostats

Traine perfect fit 5" whole house media filters

Ducting of all bath, dryer, and kitchen exhaust fans

All other labor and material to complete the job

Proposal does not include high voltage electrical

Bid B ($23,835):

Upstairs:

Carrier Infinity 16 seer 3 ton Heat pump (includes Infinity thermostats)

New R6 flex ducting 9 supplies and 4 returns (includes all grills and registers

Media filter for system

Downstairs:

Carrier Infinity 16 seer 4 ton Heat Pump (includes Infinity thermostats)

New R6 flex ducting for new area 4 supplies and a return (this includes all grills and registers)

New metal insulated duct work under house to floor registers (6 supplies and 2 returns with all new grills and registers)

Media Filter for system

Additional:

Additional work needed digging out needed area under house to allow for duct work to be installed as needed.

Digging of a trench from the house to the area that the condensers will be installed at including the needed PVC and copper.

So, those are two of the three bids. We know VERY little about any of this, so any advice would be greatly appreciated! Thank you so much!!!

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Comments (2)

tigerdunes
12 years ago
Jen

these are the minimum specs you should be looking for.
both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset
10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.

How is this home being heated now?

Heat pump systems can be problematic in old home's that have poor insulation qualities. I would hope within economic reason this is being properly addressed in your renovation project.

The size of systems quoted raises questions. I would insist on load calculation broken out for each floor/zone.

Ductwork insulation should be no less than R8. There should be dampers on all supply runs.

On the Trane quote, I would want the XR15 HP model.
Thermostats matter. I want to know the model number Trane quoted as well as the Hyperion air handler mdl number.

Those are my initial thoughts.

IMO
energy_rater_la
12 years ago
Can't really improve upon tigerdunes minimun specs above,
efficiency performance dehumidification (if sized correctly..)staging electric strips.

R-8 should be for all ductwork supplies and returns.
All connections should be mastic..not foil or duct tape but
paint on mastic and/or mastic tape.
load calc to show how much air is needed
and how to distribute air.(duct sizing & design)
I'd invest in the room by room load calc and
see how they plan to size the ducts and lay them out.

you don't mention where ahu & heaters will be located.
one in crawl space the other in attic?
both in conditioned space with ductwork in attic and
crawl?

one thing to know going in is that sheet metal duct is best under houses. animals love flex duct, while you can
usually deal with mice in attics..coons, possums can wreak
flex duct.
also sheet metal duct ( I call it hard pipe) leaks air at all connections. in addition to screwing duct together
all joints and seams should be mastic sealed...before
duct is wrapped. duct wrap should be stapled, and taped with duct tape (fsk tape)

80 years ago we built houses for ventilation.
tall ceilings, balloon framed walls.
to add central air to these homes is to change
the dynamic of the house.
in my area we usually foam floors with closed cell
as it is the most cost effective way to both air seal and
insulate the floors.
here is a link to LaHouse (LSU Baton Rouge, La) about
insulating floors:
http://www.lsuagcenter.com/NR/rdonlyres/D33F711D-DC4B-4E4C-9ED6-A97DCE9DB026/79806/pub3187insulatingraisedfloorsHIGHRES.pdf

you'll have to cut and paste for it to work..

if ductwork is in attic, another option is to foam the roofline and keep ductwork in a conditoned space.
this will minimize problem areas like recessed lights
that are not air tight, which allow attic air and insulation particles to enter the house.
we use open cell installed in rafter bays and covering the
face of the rafters.

in my experience with older homes you have to fix the house
in terms of air leakage and insulation for the central installs to provide comfort, dehumidification and savings.
otherwise you just throw more tons of a/c at a leaky
structure.

insulating floors and attic would be to your benefit.
air sealing the house is a good investment.

there are lots of energy raters in Texas.
you should talk to a few and get more information before
spending so much for a/c.
unlike a lot of audits an energy rating
unbiased information that provides a blue print for efficiency, recommendations specific to your home
and performance & install verification.

best of luck.
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Adding A/C and HP to 80 year old home! Big difference in quotes!

Comments (2)

tigerdunes

energy_rater_la

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