There are software programs that HVAC companies can use to calculate heat gain and heat loss. A good company will do a load calculation as part of an estimate or after you sign the contract.

Mine cost me right at $400.00 but my distributor CooP'ed 50% of it so it was pretty inexpensive. Check the link below.

Here is a link that might be useful: Manual J

In NY when I was working it was required for a new install (Man J Ht loss/ht gain). Anyone contractor in my eyes that does one professionally and upfront and gives it to the customer before a contract and downpayment wont be in business long. A proper one takes time and costs billable hours to just give away with a quote.

Same thing for duct design, a proper design and material list can take 2-4 hours, why turn it over to be shopped?

i charge 300 dollars to do one but i tell the customer hat to give me as far as window's door's insulation. which way the house is facing....

How do you talk to a customer's hat?

I think he meant to type "what."

So zl700, if I understand you correctly, you are saying that you only feel that one is necessary if it's a new construction job? I can definitely see logic behind this, but the problem I see is that perhaps the home was incorrectly sized from the getgo. I don't disagree with professionals who do not want to do a load calculation for fear of wasting time and losing the bid. Many times I'm sure it's evident to the homeowner if a system is incorrectly sized. But if the homeowner expresses concerns and the professional has doubts regarding sizing--that's when I'd think the load calculation is necessary.

In NY it is a requirement in order to pull a building permit that involves a heat/Ac install to provide a Heat loss/gain.

My feeling is that it is always required.

Perfect example is on my dadÂs house built in 1968. It had a 140,000 Btu boiler. So did every other house on the street, ranch, split, big, small When I put a 95,000 in his house, I heard about his worries until about February, then he ceased. Back when energy wasnÂt a concern the builder/HVAC guy used the one size fits all. In 1968, I canÂt blame them, who cared.

I will confess though that with exception to special circumstances, a person like myself that has seen or done so many, can do one in my head in about 5 minutes and be within 5% of the long calc process. Call it experienced.

However there are many people that try to do the same and end up so wrong.

My point is why should a contractor do a free one and hand it over to the prospective buyer to be shopped and beaten by a low bidder that used the results.

This has always been a big problem in HVAC quoting, especially with radiant designs. Radiant requires a design to determine size, but more importantly materials and labor. Why should a contractor do all the work to just hand over the layout to the homeowner?

If a former customer wasn't willing to pay big for the design and be rebated with a contract, he didn't take me or our company expertise or experience seriously in the first place.

The manual J heat gain/heat loss calc should not be a competitive bidding issue, or costly problem.

Because too few HVAC contractors' are doing heat gain/heat loss manual J calcs, the energy heat gain/heat loss manual J calcs should be part of elementary & high school math & science curriculum.

Every home should have an accurate documented energy calc available to the home owner & any HVAC contractor.

This also goes for the manual S & the manual D. Our youth can change our energy waste toward energy conservation.

Our youth can change our huge HVAC energy waste, toward energy conservation.

There should also be many adult education training sources for them to learn & do the preceding, fun based, energy conservation chores. These programs need to be on the county, town & township level of every community.

My web page will be further developed, ASAP.
- udarrell

Here is a link that might be useful: Proactive Government HVAC Energy Conservation programs functioning at the local level

zl700 is correct. Several years ago, i thought to get a very accurate list of my materials, i neded to do a load on the house ( for the equipment size) & go ahead and draw out the duct system to get a feel for the cost of the board, flex, number of ins. boxes & register and so forth. Usually what would happen is my customer would then get someone else to install Goodman equipment(im not brand bashing) using my load, duct design, and time.

Basically what i have been doing now is asking the customer alot of questions about their old system, find out how it cooled, compairing btu outputs from the old a/c compaired to what the new one will put out, if they were overall comfortable, uneven temps through out the house and so on. With this i can make an educated decision of the new equipment to be installed. On homes with problems, i do loads but i never give out the results untill i get the job.

IMO

In my case I'm going to be changing a lot about this recently purchased (never lived-in, old) house like vaulted (insulated) ceilings and new windows, so I told the contractor that everything should be done before changing the furnace and adding an AC in order to do the tests to size it properly.

But the HVAC person I spoke to who the contractor uses, and has been doing this for many years says no tests are needed as they can determine better by experience, which I find odd based on what you all are writing here. And $4000 seems like highway robbery compared to those $400 numbers I see. Maybe Nor Cal bay area is just way more expensive than elsewhere.

i could see charging to do it and then takign that charge off teh final cost IF you bought it from them. no sense in giving away their time.

around here when they run one they show you the info, but they do not GIVE it to you until teh system is ordered. they also do not charge a fee to run it either.

I guess HVAC people in the SF bay area are less informed than elsewhere in the country. Oh well.

No No... I think you misunderstood me. The pc software cost me around $400 for just the manual J. I dont charge that per home. Residential loads are around .10 cents per square foot.... so a 2500 sq.ft. home load should run around $250.00

$4000 for a home load is unreal.

Hope this helps

Wow, and my home is under 2000 sq.ft. Gotta love the cost of living here. Maybe because it doesn't get too hot or cold that the HVAC companies aren't as good as elsewhere.

We paid a 3rd party to size our system and lay out the ductwork (new system, old house). Cost was similar to what fluffybunnysui mentioned- $0.10/sq ft. So you might be able to find someone in the energy rating biz to do that, then shop it to contractors.

That said, the hack who ended up installing the system (brought in by hack GC) fought me a lot on doing what was set up by our energy rater. I held fast and (after I fixed all the leaks in the hack-installed ductwork) the system runs well, doesn't cost a ton, and keeps us comfortable.

Hack HVAC contractor wanted to use rule of thumb for sizing. And said he didn't do Manual J b/c doing all those calculations was too time consuming. Reality is that w/ the software it takes a couple hours at the house to grab all the data and maybe an hour to enter and to run the calc.s. My guess is that the software is paid for after 3-4 jobs.

I'd run the other way from someone quoting you $4k, even in NorCal. Not just b/c of the price but b/c I'd wonder how careful an install job they'd do if they didn't care about getting the sizing right.

$4,000 for a P.E. stamped set of plans residentially is not out of the ordinary however; most often unnecessary.

yoyoma--
I'm on the Peninsula and have had four estimates for new furnace and A/C. Not one company offered a Manual J. When I called one of the "final two" with questions, I asked whether he'd done a Manual J. He said no, that they only do the Manual J for larger homes (above 2800 sf, I believe), particularly if it's two-story or multi-zone. Otherwise, they just go by experience for the smaller homes (my place is 1500sf).

and going by experience is not always the best thing.

lots of hvac contractors here use 400 to 500 sq ft per ton.
I'm sure they do it everywhere, but it doesn't make it right. these units are oversized, cost more to operate, don't dehumidify, and have shorter useful lives.

I hear you Thull..have had many arguments with contractors
about energy rating upgrades. builders, insulators, window
installers and manufacturers..its tough getting people to do the job correctly sometimes.

Load calcs shouldn't be given in detail until a contract has been signed or load calc paid in advance, IMO . An example I give, is that the city that I live in, called and asked for a bid and it supposedly wasn't a public bid. Since we do a lot of work for them we did load calcs ,as it was a big job and gave them specs. Next week, a posting in the local paper specifying what we had told them we thought they needed and it was open to all bids. Lost the job and time. A few months later they called wanting another bid for another project. Sorry Charlie.

Tin Man,

Same thing happened to me as reputable HVAC mechanical contractor as a young man; I gave a quote to a small municipality.

Then found out later they invited a group of contractors to a pre-bid meeting about the same project through a fellow ethic competitor.

When I showed up and signed the attendance and info sheet, when it got back to the buyer, his expression when he recognized my name and co. was the best.

At that point, I handed out my quote with scope and pricing dated 6 weeks earlier to all in attendance and made a quick statement to all about the improprieties and walked out.

Not sure what happened after that but I was satisfied.

yoyoma... I have no idea why you would insist everything must be done in advance before the load calcs are done. If you know the insulation being applied, the windows being redone, etc., then you know all surface areas and R-ratings. You know directions faced and lat/longitude. You know the door types you may replace. You know the sq. footage and living area sizes. You know everything that is plugged into a man J and man D.

How do you think that all this is done for houses under construction? It's all done well before completion. Ours was done after our plan/products finalization was done.

I can imagine that being in any jobber biz you're eventually going to get shopped after quoting a job. In my business, we take that risk by submitting our best ideas on multimillion dollar public works projects. They may like your idea but not your price, and you spend tens, maybe hundreds of thousands in the pursuit over multiple years. Think that's just a lack of ethics that pops up across the business community.

Energyrater- I've been participating in a discussion on FH's Breaktime forum. Someone putting in vinyl windows where the mfr instructions said not to foam them in. I was shocked by the number of folks who agreed that you should follow the directions and use fiberglass. I can't imagine putting windows in and not using the window/door poly foam to seal them in.

dallasbill- the only thing that you'd need to wing it on is the ACH. If the house remodel is in progress, you won't really know how leaky it's going to end up. We did a blower door test before construction and then based the sizing on an estimate of how leaky it'd be after doing lots of improvements. Still have work on weatherstripping old windows/doors to do. I'd intended to get it tested again afterward, but we'll see if that actually happens.

yoyoma- ideally you want to test the new system with a "duct blaster" test to see how well sealed up the ductwork is. Not as big a deal if it's all w/in the conditioned space, but most of the time it isn't. A well-installed new system will leak .05 cfm/sq ft of conditioned space.

Here is a link that might be useful: Southface fact sheet on blower door & duct blaster testing