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# HVAC Performance Comparison

Hey everyone,

I'm a software engineer that is starting to think about building a house, and my research into the subject of the best HVAC system for my house brought me here. I tried figuring out what HVAC system would be most cost effective in my future home, and so far I understood that it is a complex question with a lot of variables to consider.

I'm wondering if you could recommend any materials for someone who is a Building Energy Modelling newcomer, but who would like to understand how I could model different setups for my future house? Any reading materials that could help uunderstand this subject, or any tools that might be helpful. So far I stumbled upon OpenStudio which looks like the tool that might help me out, but I get a bit lost around the building library components.

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Hi - this is something that takes a bit of knowledge and experience to assess, although there are some guidelines to help and most likely won't need much modelling other than simple back-of-the-envelope calculation. I think using OpenStudio might be a bit too much for your needs?

There are two key concepts you need to consider, with one being heating/cooling capacity (imagine horsepower for a car) which you'll pay up front and the other being operating cost (e.g. like gas/oil change etc). In HVAC, the capacity is measured in 'ton' (1 ton = 12,000 BTU = 3.5 kW). So you need to estimate how much heating & cooling capacity your house will need and compare the upfront installation cost and the operarting cost over some reasonable period (say 10~20 years).

Some food for thought:

• In general, ground source heat pump system is the most expensive in terms of heating/cooling capacity (> $10k/ton), but most economical in terms of operating cost. In terms of overall lifecycle cost however, not really worth it for most homes. • Air-source heat pump will also be somewhat expensive to install (~$3k/ton) but If you live in moderate climate (e.g. San Francisco), operating cost can be competitive with natural gas. Note that the bulk of the total installation cost (~2/3) is actually labor cost, with equipment cost only about 30%, so you'll get a lot of variation in quotes. Unfortunately, very few contractors will give you a cost breakdown.
• If natural gas is available, gas furnace will be the cheapest in terms of capacity and for most places in the US, also cheapest to operate, although not terribly much cheaper than air-source heat pump. For new homes, this will require ducts to be built also.
• Most contractors will quote you a system that's much larger than what you need.

Not sure if this helps but I've seen a lot of people get lost researching this so hopefully it's somewhat helpful...

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Hey Joseph, thanks very much for your response, it is very helpful! One more followup question if you don't mind. I'm wondering if you know if air heating system or water heating system is more optimal? I'm trying to decide if I should use an air to air heat pump, which can both a heat & cool, and my house would use air vents to distribute the heat. Or if I should go with an air to water heat pump, and use water based radiant heating. In the latter option it feels like I would need a separate AC system. I'm from Europe, and where I live air based heating systems are not too common...

( 2023-10-18 15:37:22 -0500 )edit

If you are thinking of radiant floor heating, that's a very good choice and would make the heat-pump system run more efficiently for heating. They're more expensive to install but if given an option, would definitely recommend and looks like there are systems that can also double as water heater. You're correct about needing a separate AC systems though. For air-to-air type, I would suggest considering mini-split types because these distribute heat more efficiently and you won't have to worry about cold/hot spots from uneven air distribution.

( 2023-10-19 12:52:56 -0500 )edit

Oh that’s interesting! Where I live (Poland), radiant floor heating is more popular and cheaper than air based heating system. I thought that air based system is more efficient. Thanks once more for all tips, that’s very helpful!

( 2023-10-19 14:18:53 -0500 )edit

You're very welcome! Yeah, installation cost varies according to how common the system is in that area I think. For instance, mni-splits are super cheap (& easy) to install in Asia but in North America contractors charge premium. Glad you find it helpful - best of luck!

( 2023-10-20 08:15:35 -0500 )edit