I'm ready to make the change to geothermal HP for my 2,300 sq ft (1st floor) home but two local contractors' approach to sizing has been "Whatcha got now?" The 17 year old 5 ton split HP was installed in a vastly different house, no insulation or insulated windows, etc. and was a complete by-gosh and by-golly buddy deal at the time so I am very uncomfortable with these guys' approach now. The local power company suggests I talk to more HVAC contractors, one who sounds like he knows what he's doing says he can take a look after the New Year... What heat gain/loss calculator is 'relative newbie' friendly so I can get a handle on what my needs are. I understand the installation and HP principles (I've done a few regular HP installations myself) but I want this done right the first time! Thanks.

HVAC Calc, a pro package but fairly easy to use, offers a temporary 60 day license aimed at homeowners in your situation. $50, last I heard

The one I used to check behind my installer was HVAC-Calk
http://www.hvaccomputer.com/
It was very easy to use, I watch the demo, paid $49 for 60 days, loaded my data in about 2 hours, and by the time my reg code showed up I was ready to run the numbers. I had several data points from live measurement I had taken @ 24F and 100F and this program was within 1000 Btu's for heating and cooling.
I had also made some changes to my house (finished the basement and added it as conditioned space, replaced some sliding doors, and added 18in of insulation to the attic).
My old air source HP was 2.5T and the program came up with 1.6T, and my new Geo is 2T 2 stage and works great.

HVAC-Calc matched another package, RHVAC, to within 5% in my experience

Are there any energy audit companies in your area? As well as the data to enter into the software the results of a blower door test and other variables identified by the energy audit company will help you fill in the correct info on the software for your house.
Eric

WP is right as usual, but a load calc with reasonable values for building tightness and infiltration should get you close.

Load calc is only half the battle. You don't want to get a good manual J and then follow it up with poor design.
You might want to share the results here.
Joe

HVAC-Calk sounds like a good start. The local REA does energy audits but I'm not sure about their schedule, next Spring won't do me any good. It's a 19th century commercial building so it's far from airtight!

There is a river of tears on the net about older structures with botched up load calcs and the resulting issues, my farmhouse included in that river. Adding the fact that it is commercial space adds a whole nother variable if you have walk up customers to add to the load. We recently helped fix a huge liquor store that the hvac had used residential software for the load calcs, they were way off. Failure to meet demand in heating or cooling. I would definately PAY for a independent energy audit from a company that it commercial old building experianced prior to moving forward.
Eric

Well, it's a commercial space in the sense of it being a depot but it's used as a home now. It's that the construction methods differ from 19th century homes in the area as the wall framing is post/beam, the siding batten on board and the warehouse floor in the back is 2.5x9 cypress that's been 'caulked and paid' to seal the cracks, if old houses are drafty, old depots are windy! In fact, most of the initial work in that department was to keep critters out more than seal the building for any efficiency, much work has been done in the years since but it will never be like new construction!

Posted By abh3 on 18 Dec 2010 06:08 PM 
much work has been done in the years since but it will never be like new construction!

True, in some regards it may have advantages. That's why you need a good evaluator vs on line speculation.
Joe

Posted By abh3 on 16 Dec 2010 04:48 PM
The local power company suggests I talk to more HVAC contractors, one who sounds like he knows what he's doing says he can take a look after the New Year... What heat gain/loss calculator is 'relative newbie' friendly so I can get a handle on what my needs are.

First off, you are to commended for being concerned about getting this right. That being said, surely you're not going to let a wait of 3 or 4 wks control how you approach an issue, the results of which you will live with for 20 years, are you? Is it possible that the reason the one contractor can't get to you until after the first of the year is because he is good, and trustworthy? Isn't the one you want then?

Big difference between a true professional HVAC calculation by a competent contractor vs. a very good DIY program like HVAC Calc, is detail. The most widely used pro program is by Wrightsoft. It will give you room by room, wall by wall, heat calcs. I used HVAC Calc, but it wasn't until I got the output from Wrightsoft that I could determine how much heating/cooling needed to directed to each part of the house. The overall numbers from both programs were reasonably close.
Wrightsoft has many more input and output options than does HVAC Calc. The old adage, you get what you pay for, applies. HVAC Calc, even in the pro version is only a few hundred dollars. Wrightsoft is several thousand. That's one reason why your average Joe AC Man doesn't have it.

For 50 bucks HVAC Calc is a good investment because it will give a great start down the path of a reliable heat load calculation. Just don't stop with it.