Heat sizing question

Why not do the Manual J calculations? For a structure like that they would take perhaps half an hour…

South Texas?

The correct answer is to perform a load calc

Well insulated and sealed buildings built to today's codes should be in the 20 or lower number

Oversizing equipment is a bad deal deal for fuel consumption, excessive cycling, and low return temperatures

ACH on storage or warehouses could be a big number.

I used to do a lot of work in southern NJ. I ran my own company then sold it and worked for another contractor. That contractor required the estimator to include a manual J load calculation to accompany the heating equipment size we put on our estimates. Then another contractor I worked for also required the load calculation to accompany the equipment selection for the sales contract. No calculation, no approval of the work. this protected their customers form a lazy salesman that was not going to take the time to measure up the home and specify using an arbitrary rule of thumb. then I operated my own business again. For over 35 years of working in southern, NJ every job that I quoted a new heating or air-conditioning system for has a manual J load calculation in the file with the sold contract.

I can tell you from experience that selling a smaller heater or air conditioner than the competition that uses your method for sizing equipment was very successful for me. the prices came in lower as a result of using lower price equipment, (the 40,000 BTU unit was always less expensive than the 80,000 or 100,000 BTU unit of the same model equipment). Then when you needed to match up ductwork for the larger oversized equipment, or the pipe size for the larger boiler, they always came in higher with the number if register outlets and trunk duct sizes or pipe fittings on the boiler jobs.

If you are going to do this for a living, you need to learn how to do heat loss calculations, or hire someone who does. And NJ and MD are in the same climate zone and I don't remember any of my heat loss calculations for a standard residential home being anywhere near 30, BTU per sq ft.

How often are the warehouse doors opening in the winter? 10% 0r 50% of the time? what insulation is in the walls? How many windows are in the walls? Glass looses more BTUh per sq ft, than an insulated wall. So you 30 BTU per sq ft may be right on, or way off. Tough to tell.

I was doing my own whole house load calculations in 1980. It's never too late to start to do it right.

not so much. I had an interesting strategy. I would ask the potential buyer if they expected to get more than one estimate. (and encourage them to) Then I would measure all the rooms and windows etc and enter the info on a sketch pad. Sometimes I asked them to help hold the tape measure. During the conversation I would explain the process of the heat loss calculation. Build up a friendly relationship. Then I would let them know that I would go back to the office and prepare the load calk and then the estimate.

Just before I would leave I would ask if I could be the last one to return after all estimates are collected That way the competition didn’t get that chance.

When I returned, I would sit with them and answer every question until they finally decided what they were going to purchase. Usually, it was something that I offered

There was one occasion when my competition forgot to include a chimney liner and their price for doing the same job was significantly lower. that he was reputable and that he would stand by his price even though he made a mistake. I recommend to the customer that they purchase this job from my competition. I later saw my competitor at a house and told him that I bid on that same job and he told me he lost money on that project.

There I go, off on a tangent.
Anyway, being the last guy there I was pretty much guaranteed the sale