hello, we are in the process of building a custom home and I have to choose the HVAC sub-contractor. I have received bids from 3 different contractors. In trying to resolve differences in approach I am getting many conflicting answers, and I am now thoroughly confused. I'm hoping you can help me determine who is correct.
As background, it is a two story house. We are planning to do radiant heat on the 1st floor, and hi-velocity or forced air on the 2nd floor (except for tiled bathrooms). The hi-v/forced air duals as heat in the winter and A/C in the summer. There is also limited ducting for A/C on the 1st floor for cooling in the summer. House is about 9000 sq ft, 2nd floor has 9 ft ceilings, 1st floor has 10 ft ceilings. Also, we live in Seattle, so we have very hot days for about 3-4 weeks per year, and very cold similarly, but in between it's average. I am told this means it is a reasonable/good idea to focus heat on the 1st floor and A/C on the second, and only secondarily heat on the 2nd floor and A/C on the first.
Here are the issues. It'd be great to get answers to each so I can figure out who is giving me good answers.
1. Hi-velocity vs forced air. One person says that Hi-velocity is the way to go because heating the 2nd floor with will require "pushing" air away from registers in the high ceiling and forced air won't be good for that. For A/C they are equivalent. Another contractor says it makes no difference in comfort, and that Hi-V is just more expensive.
2. Zoning Hi-Velocity. Plan was to have 4 heating and A/C zones. 3 upstairs and 1 downstairs. One contractor says you can't zone Hi-Velocity, one says you can zone it no problem, and the other says it is not recommended because people mess it up but is ok if you know what you're doing.
3. A/C capacity. One contractor is proposing 2 5 ton units (1 each floor). This person says that we "need every bit of 5 tons each floor". Another is proposing 1 4 ton unit. He says the house calcs to 8 tons, but that a 4 ton unit will focus on the upstairs first (which will also benefit the first floor), and then supplement the 1st floor in its "spare" cycles.
4. A/C in parts of first floor. One contractor says we should run A/C to the whole first floor because otherwise it will create drafts. Another contractor says it is fine to A/C just portions (the large open areas) of the downstairs.
5. Chillers. One contractor says that the distance between A/C handlers and condensors cannot be more than 50 feet or they will lose efficiency. His solution is to use Chillers. Another contractor says 75 feet, and it's not an issue. Another says that chillers are not worth the money and only useful in commercial applications in the practical world.
6. Area over garage. We have a wing of bedrooms over the garage. One contractor is telling me that the area of the garage will not be affected by the temperature of the garage (because of the heavy insulation in the garage ceiling), and one is telling me I need to either radiant heat the garage or do a radiant floor in that whole wing.
7. Hot water heater. One contractor has proposed two 120 gallon heaters. One has proposed a 100 gallon heater. Another has proposed an 80 gallon heater. The last one says the 80 gallon heater is rated to 269 gallons in the first hour and that this will be plenty of hot water - figure maximum of 5 showers going at once.
8. Upstairs radiant. As indicated above we are planning to do radiant in the tiled areas upstairs. One contractor says this will be *very* expensive due to having to have a manifold per bathroom. For example, we have two bathrooms over the garage that are 50 feet apart. he says they need a manifold each due to distance.
9. One contractor has proposed a Viesman boiler, one contractor a Polaris or Triangle Tube, and one a York. The one proposing the York says the Viesman is barely better in the practical world and that it is more expensive due to bells and whistles only. I will want to eventually be able to automate the heating through a home auto system, so I need the ability to control the system somehow, but I don't need the boiler itself to be smart. He says the Viesman has things like ability to set a "party" setting for when guests will come over.
10. Piping/controls. Two say Wirsbo only, one says he has an equivalent product that costs less. Two say Tecmar controls, one says I need a different brand (sorry I forget the name) for home automation.
11. Heat pump. One person recommends a heat pump instead of the forced air or hi-velocity on either floor, with the idea being that the heat pump can do heating or cooling. He says there is a model that is really good that won't make much noise ("can barely hear it from 6 feet away"), and that it also means the fuel source can be either gas or electric.
Needless to say, the actual price from these contractors varies greatly, and I'm having a hard time deciding who is on target with their proposals. Any help you can give would be *awesome*!!!!!
1. I'm not a fan of Hi-V. Lowers SEER considerably and lowers capacity. For the same $$ as the Hi-V air handler, you can get a variable speed AH that boosts SEER and has constant low speed fan for circulation & filtration.
2. I wouldn't think it wise. Hi-V runs about 1/2 the normal airflow and if you start zoning beyond that, you are barely moving air over the coil and will cycle on freeze-stat.
3. How are they deciding that? 4 tons vs 10 tons, that's wild. Ask to see their calcs.
4. My cousin has a large house with standard A/C in the attic. Only 2 supplies run to the first floor cuz her Mom didn't want to see registers in the public areas. The 1st floor stays very comfy in hot weather just from the cool air falling and warm air rising to the 2nd floor. House has 1 3 ton unit, one other bid they got (20 years ago) wanted 2 units totaling 5 tons.
5. Height rise coupled with length could be a problem but overall 50-75' is acceptable for refrigeration piping. Manufacturer's instructions need to be followed carefully.
6. Well insulated garage ceiling will keep above it very comfy. Heat as you would any other living area.
7. Are these indirect tanks heated by the boiler? You need considerably less storage capacity than with conventional tanks. 269 first hour recovery is more than 4 standard 40 gallon tanks. That is a lot of hot water!
8. Look into electric radiant for those small rooms. Doesn't use much juice and far cheaper to install.
9. York doesn't sell boilers. Viessmann is the Rolls Royce of boilers. If budget permits, super. If not, there are others for less. Not familiar with the other 2 you mentioned. Buderus is a good boiler.
10. No idea
11. I'd go heat pump. That way in mild weather you don't have to heat the radiant just to take a little morning chill out of the air. Also, I'd guess electric rates are cheap there and a good heat pump would be a fraction of the cost of even a good gas boiler to run, BTU for BTU.
#1 Hi V does a very good job mixing up the conditioned air which would work well for heating from the ceiling or AC from the floor. Yes it is more expensive. I would bring up using panal radiation and just use the ceiling for AC....
#2 Zoning AC , I would like to know more about zoning HV.....Variable speed blower ??? I can not answer , don't know.
#3 Ask to see their calulations and ask how they arrived to them...
#4 perfict designed air condition reaches and moves the air from all the dead areas
#5 I'am not big on chillers for the home, dehumidification is important....
#6 The rooms over the garage woud have higher heat loss then the main house and needs to be zoned......Radiant would be nice....
# 7 Hot water need is your largest load. This is more up to the Lord of the home. IF you want to run 5 showers at once, say the standard 2.5 gpm shower head for 20 min total you need 5x 2.5 gpm x20min =250 gallon water heater...... Tell them what you need.
#8 Radiant in a tile or stone bathroom , yes! Yes you need a manifold for each bathroom. Radiant heat in mass floor or wall is top shelf and will give your family comfort....Yes it cost's more
#9 From that pack .....Viesman.... Polaris ? don't they make snow mobiles ? Don't know about them on the East coast.....
Fwiw, we (in Michigan) had electrical radiant heat installed in a tiled 2nd floor room over cold (our entry porch). The electrical was cheap, but it didn't put out much heat.
We took out the porch ceiling below and installed pex, etc, with a small boiler. We LOVE the result.
Our house is a combination of geo forced air and gas radiant. I disconnected all the electrical radiant.
Not to mention, there apparently is a short life for the resistant wiring (10 years or so).
Brianmu,Did you mean to say
a 9000sqf two story?
Also I use the Vermon
Castings fireplaces and
stoves.I can tell you
that there comfort control
is werth every penny!
It is the only direct
vent I put in.Why? there
flame pattern is great.
the remote control works
well and is fairly intuitive.
AND I have never had a call
back or complaint with them.
Also I live in kinda the
same area as you.After you get
your heating and cooling loads.
I would highly suggest that
you have somone prove that
gas is cheaper than eletric.
It is somthing I have thought
about for a long time.I have
been playing with some of
the programs out there
looking at rate of returns
for upgrading equitment. and
found that eletric is not
far off.In are area what
do you think will go up
the most.Remember we have
dams around here.
41gasman
Tekmar is the best there is in temperature control imo.As for the guys that insisted on wirsbro pex.I have to say wirsbro pex is good but not the best ask them to check into rehau pex.I would NOT use anything less than rehau or wirsbro for my own home.Given the choice of standard duct over hi-vac I would say standard duct any day of the week.baldie wrote up pretty decent reasons as to why.Proper pex heating is a different animal than putting some tubes in the floor.I would not use a contractor that was not experienced at it.
With such a large house, I would look at the multi-city system from mitsubishi http://www.mrslim.com
You'll get multiple smaller zones to heat and cool at the same time if you need to. Go with a gas radiant system and indirect tank. Kick the radiant on when winter sets in and use the heat pump for the cool mornings where you might just need spot heating for a few hours.
here is info on our fuel source costs from the city. Sorry, the table gets messed up pasting it but the central furnace corresponds to the 60-90% columns, the electric resistance furnace to the 100% column, Heat pumps to all the HSPF columns. The electricity values are empty for the central furnace columns, and the natura gas and oil values are empty for the resistance furnace and heat pumps.
Fuel cost comparison:
price per therm* for various fuels
Central furnace space
heating efficiency Electric
resistance
furnace Heat pumps
Fuel Price 60% 80% 90% 95% 100% HSPF 6.8 HSPF 8.0 HSPF 8.5
electricity (per kWh) $0.0866 $2.54 $1.27 $1.08 $1.01
natural gas (per therm) $0.8060 $1.34 $1.01 $0.90 $0.85
oil (per gal.) $1.59 $1.89 $1.42 $1.26 $1.20
A heat pump at 47 out costs $7.87 for a million BTUs
A 80% gas unit costs $10.13 for the same heat
So instead of getting straight cooling, if you got a heat pump for mild weather instead of firing up the boiler and all the radiant tubing just to take the nip off in the morning, even with your average juice rates and good gas rates, you can save.
Even a condensing boiler would cost a hair more to run than a heat pump in mild weather. What's very cold for you? For us it is -10
Brianmu,It is kind eye opening
is it not.If you have a looksy
at yourload calulations and
add up the needed btu's for
the year you will see how
much money you will save
heating your house.So
if you go with a split
system and bag the high
velocity suff.you will be
living large!Also make sure
in the load calulation that
they have room by room cfm
requirments.This way they
will have the info for
proper duct sizing.
Rule of thumb get used
alot.
Go with HARD PIPE the
system will love you
forever.And it can be
effective cleaned later
down the road.I hate to
say this but flex duct
is really abused around
here.ALOT.Make sure they
size ducting for a/c
cfm.Most just call it
good for heating cfm.
Let see if theres a way
that you can tell me
what company you are
useing.I'm very curious.
Thanks 41Gasman
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2story house
Fuel costs
