# What size HVAC Unit???

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#### Krich

##### Well-Known Member
In the barndominium I'm planning, the house itself is about 3,000 square feet and I'm wanting to install a whole house heat pump (will have ducts in the attic feeding air to each room)

The center section of the floor plan has a living room / dinning room / kitchen that are open to one another... and then there are 2 master bedrooms (with walk in closets) and then their's a separate home office

I see the Seerr ratings are around 17 maybe 18... but how many "Tons" should be enough for a 3000 square foot house?

It depends on more than just the square footage. The volume of the house, orientation of the house, windows, insulation, and local climate.

This might help HVAC calculator I haven't tried it though.

Thanks for the link... I tried it and it's just throwing out a price estimate and says nothing about how big of a system I should get.

So what is "volume of the house". Also, I'm down south where late summer temps get to 105 degrees or even slightly higher than that sometimes.

A house is a three dimensional thing. Volume would be length x width x height. So higher ceilings and vaulted/cathedral ceilings would have a bigger load impact than 8' ceilings.

For heating, this is where hydronic heat in the floor is really neat. I puts the heat at your feet and gently rises keeping your feet warm as you walk around on a warm floor. I was working in our church, also in the south, in the summer. I was on a ladder in the high ceilinged sanctuary and it was amazing how hot it got once I moved 8' off the floor. The cool air does tend to stay low and the heat rises. One of the reason older southern homes had high ceilings, and transomed windows over the doors. Get the heat up higher in the summer before AC was invented and widely used.

OK, so length x width x height of the house is.... 81 feet long by 38 feet wide with 9 foot ceilings

So you have 27,702 cubic feet to heat and cool. The type of construction, insulation, windows, shade, and orientation all have an impact on the HVAC load. I'm sure there are software tools and/or websites out there to plug in all the factors and get it to spit out an estimate. They may be fee based and not free. A HVAC company would be able to calculate it out, and I'm fairly certain they have tools to do it.

I guess once this all gets constructed, I'll have a few local HVAC companies come in and provide estimates and then I can see how many tons they are recommending for the space needing to be cooled and heated.

THEN, I can go out and buy the system I need and shop around for a qualified HVAC guy to install it so I can get the warranty offered by the manufacturer.

They all seem to say warranty is only applicable if qualified service people install it... and then they turn around and tell people it's so each to install they can do it themselves!

I guess once this all gets constructed, I'll have a few local HVAC companies come in and provide estimates and then I can see how many tons they are recommending for the space needing to be cooled and heated.

THEN, I can go out and buy the system I need and shop around for a qualified HVAC guy to install it so I can get the warranty offered by the manufacturer.

They all seem to say warranty is only applicable if qualified service people install it... and then they turn around and tell people it's so each to install they can do it themselves!
An unlicensed Technician does not "qualify" as a person to uphold a manufacturer's warranty, hence the premium you pay for a professional HVAC company to do the work. Most states even require a permit to be pulled for a change-out, and if one is not pulled, and you end up with structural or health issues in the home that insurance would normally cover, it won't.