18,000 S.F. home - where to begin?

[paulnj1976]

I have begun the design process for a new house, which will be about 18,000 total heated and cooled square feet -- main house (first and second story) are approximately 11,000 S.F., attached garage 1,000 S.F., finished basement 3,000 S.F., and finished attic (third story) 3,000 S.F.

The house is in New Jersey. I desire radiant in-floor heat, and central A/C with all supplies on the ceiling. There will be many coffered ceilings, so I'm thinking there will need to be a lot of those "strip-style" diffusers that blend in nicely with the mouldings.

First question... should I be getting a commercial HVAC contractor in here? I want a top-quality job, nothing that I'm going to have to go back and "revisit" after it's done.

Second question... I'm confused about whether I entertain the idea of one big air-cooled chiller with several air-handlers for the central A/C, rather than have like 10 individual split-systems. However, with a chiller and air-handlers, can you get the same effect as with a two stage compressor and variable speed blower (for excellent humidity control)? Really good humidity control is really important to me.

Third question... with the in-floor radiant, I'd like nearly every room to have its own control, BUT, I don't want to have to go around to 30 thermostats when I want the heat on... is there any type of control system out there where, from one "master" thermostat, I can set all the heating zones to, say, 68, and then use the individual stats in each room as an override? And also see what all the stats are set at from the master, and change them from there?

I know I need to get a really good professional in here to make sure it gets done right, but as the house is still in the planning stages at the moment, I want to make sure I do my homework to make sure I get the right people in here and know what are and aren't good ideas. So I'd really appreciate any feedback. Thanks!

-Paul

[Shophound]

18,000 square feet? That's humongous!

I recommend you hire a competent mechanical engineer for a project this size. There's too much at stake with a structure this size for the HVAC to be done by hacks or "rule of thumb" contractors.

I visited a very large house under construction in Dallas awhile back. It used a chiller for the HVAC. Multiple air handlers everywhere, one chiller unit on the ground. Complex system, but apparently for the homeowners, budget wasn't a primary issue given the extravagance of the structure.

That house could easily be gutted and reappropriated for an office building...it's huge!

[Jultzya]

First, you better do a lot of research on the contractor you decide to go with, otherwise you could end up with a complete nightmare!

Second, multiple systems will insure you have heating or cooling if a system does happen to go down.
(sure, part of the home is going to be hot or cold, but not the whole house)

Third, humidity control... variable speed blowers with a thermidistat of your choice.

Forth, the system can have a 'master' control with several 'remote' stats... it's all in how you want the system designed to function (with money being the only factor). They do make stats that have remote 'temp sensors' so you can adjust the temps from one main location.

[dexman]

I'm with jultzya. I done one 14000 sq ft two years ago with multiple systems and have heard no complaints so far. If the big chiller fails, no cool ....nowhere

[edward301]

I agree, go multiple systems. I did a 14000 sq ft home
several years ago, went multiple systems, they have
been very happy.

About three months ago, I went with a friend who
works for a big a/c company in town, to do a pm on
a large home 27000 sq ft. I had to see a home that
was that big for my own eyes. They had 16 systems,
all Rheems, 8 on one side of the home, 8 on the other.

He said they were installed 5 years ago, and have
had no problems. Quite a sight (the home).

[paulnj1976]

If you go multiple systems, how can you avoid having like 10 thermostats? Can one control system control individual systems?

-Paul

[Jultzya]

There are several different ways to accomplish your goals...

One being to have one stat control close areas and have several remote 'temp sensors' that the stat figures the average temp of all the sensors.

Having the variable blowers running all the time to help eliminate temp variances (of coarse a properly designed duct system is the key!).

[docholiday]

I cant imagine you are skimping on the builder. Make sure he hires a good competent commercial design and build contractor.

Chillers will work fine. but I would have one zone run with a standard system such as the master suite. If the chiller fails, you have your haven and if the spliy system fails, I am guessing you will have a spare guest room you can crash in.

[drk]

Chiller and reheat

[teddy bear]

Get humidity control in writing from your contractor. If you want humidity control in your climate without overcooling, dehumidifiers built into your a/c system are the way to go. Get the desired %RH even without any cooling load. I spec. a lot of retro whole house dehumidifiers especially lower levels and basements in deluxe homes in the green grass climates to solve high humidity problems. Include dehumidification or leave some space for adding it on. We also do schools and other commercial buildings. Reheat is effective but a very inefficient solution for removing moisture compared to eff. whole house dehumidifiers. Most energy codes discourage reheat. Your local a/c contractor can supply, install, and service this equipment.

[Edited by lusker on 07-11-2005 at 11:30 AM]

[coco]

im only a residential tinner and that house is about 10,000 more sq ft then anything ive ever seen. im not sure about residential systems . thats most likey a commercial job. u start getting into commercial controls and they have alot more to offer. variable frequency drives to shut down individual pistons on the compressors. i took 1 yr of commercial work at a trade school 5 yrs ago so my commericial knowledge is very limited. alot more efficient to have 1 or 2 units rather than 10 like usaid.

[heatpumpguru]

We do many SUPER homes and always work with an enginner to do design,just to do alot more design than what we have time to do. We use chillers and alot of GEO,if we do not have a place to hide a chiller.I think in NJ they offer rebates on Ground sources. I can get you some names if you wish. What part of Jersey are you in?

[Freezeking2000]

Personally I would get the chiller for sure. Why have 15 seperate units to maintain. With the chilled water loop zoning is a breeze and you could have a much lower electric bill than cycling 15 units. Make sure the chiller has multiple compressors and a very good controll system integrated with your home controller.

[epacertified]

HOW MUCH DOES IT COST TO BUILD A HOUSE THAT SIZE?
dO YOU PLAN ON INVITING OVER THE GIANTS OR THE JETS?

[heatpumpguru]

I agree with the chiller,but alot of times we have a problem locating it with the outside living areas,andwho want to look at that.

[edward301]

A house that size about 7 to 10 million, more if the
finish out is top notch.

I still think multiple units, because some parts of the
house will not be used except for guests, some other
parts for big parties. If one unit quits, the others
can manage. If the chiller goes down, you are totally
out of luck.

[dan sw fl]

Originally posted by paulnj1976
begun the design process for a new house
18,000 total heated and cooled square feet
-- main house (first and second story) ~ 11,000 S.F.,
finished basement 3,000 S.F.
and finished attic (third story) 3,000 S.F.

The house is in New Jersey. I desire radiant in-floor heat, and central A/C with all supplies on the ceiling. First question... should I be getting a commercial HVAC contractor in here? I want a top-quality job, nothing that I'm going to have to go back and "revisit" after it's done.

Second question... I'm confused about whether I entertain the idea of one big air-cooled chiller with several air-handlers for the central A/C, rather than have like 10 individual split-systems. Really good humidity control is really important to me.
-Paul

Large Split Systems + dehumifiers may prove more reliable.

14,000 SQ. Feet NET may only need ~ 26 tons ( 7 or 8 systems) in N.J. .. depending on amount of glass,
house orientiation, infiltration, insulation, ..., ...

NOT All that difficult of a design task..
only Very Time Consuming.

NEED REAL Assistance,
E-mail: racingdan11 at comcast dot net

[drk]

No way would I want splits. I would go with the chiller. It is not very likely that both stages of the chiller will go down at the same time. The cooling tower can be hidden by trees a fence etc. You will need to find a good water treatment company to service the system.

[Carnak]

Or you have an air cooled unit outside.

I have seen large estate homes here with both chillers or multiple DX splits.

If you go with 15 split systems and you end up with each one of them 1/2 a ton too big,you are then 7.5 tons over sized.

Chilled water you can get exactly the righ amount of cooling where you need it.

Need to make sure a proper insulating job is done on the sprawling pipe work.

Multiple DX spilts has an automatic redundancy.

Bottom line, if you can afford to build 18,000 square feet you can afford an engineer who will design the right system for you. Make sure he has worst case humidity issues allowed for.

[biscuitnt]

Please hire a Mechanical Engineering Firm for the mechanical system design of this home. You will only be disappointed in the long run if you dont, pay out the butt for operating costs.

On the front end, it sounds like a great applicaiton for 4 pipe VAV system for total comfor control.

regards