Ask HN: Best HVAC system for a new house?

Best in what way? Efficiency? Comfort? Initial Cost? Maintenance? Air quality?

If you would like a list of resources to dive into this let me know!

If you're in a climate that gets colder than that, get either baseboard heaters, or a zoned boiler system, for backup heat for when the heat pumps can't keep up during cold weather. Which option makes the most sense will depend on how cold it gets and for how long.

Living in the Pacific Northwest I'm able to get by with no AC but need decent heat. When I lived in California, air conditioning was kind of a must but heat was pretty much an afterthought.

Ideally, engineer your house so you don't need a powerful HVAC system to be comfortable. We have (amazing) insulation so we don't need any air conditioning, but it gets a bit chilly so we are working on installing radiant heat in the floor.

Heat: the best by far is under floor heating (hot water not electric). Each room will have its own thermostat. There will be no cold spots, it will just feel cozy. No air is being cycled around the room keeping dust down.

Ventilation: indoor pollution is usually many multiples of outdoor. You want a an MVHR (or MEV) system to exchange the air in the house for fresh air with low heat (energy) loss.

AC: You need to move cold air around for this unfortunately. Pumping chilled water through your under floor heating pipes risks condensation in crawl spaces, and even if it doesn’t it simply doesn’t work very well. (Source: I had ‘radiant cooling’ ceiling panels in my last house.) I would look into a mini-duct or ductless AC system so you can control each room individually.

In climates that require heat and cooling, it is far more cost effective to go with a standard HVAC system, unfortunately, as you’ll be putting ducts throughout the house for AC. (Why put a separate system in for heating when you could just move hot air around?) But if you want the best, not cheapest, solution you really want under floor heating.

The new trends are as follows:

HRV (heat recovery ventilators) are pretty in. Basically they are auxiliary units that source outside fresh air or exhaust stale air when there is a heat differential between a specific heating/cooling zone and the outside temps. So if you are in a basement that is cold and the outside is hot it will just bring in outside air instead of turning on the heater.

Radiant floor heating and radiant cooling zones are also in. And run water through Your floors to heat or cool zones. It is one of the most efficient ways to heat a structure and feels good as well.

Geothermal is also pretty in for high-end residences but there is a high first cost to evaluate geothermal potential.

Most of these new technologies are usually coupled with standard split-systems or VRF systems and add additional efficiency (life cycle cost value) over the span of occupancy but have higher first costs .

Lastly— always consider passive heating and cooling strategies they are highest value options (insulation , shading, glazing specs , solar orientation , landscaping , etc.)

(You might get less out of this if you're in a place that boomed with air conditioning, but still there are lessons to learn from the indigenous architecture[1] of your region.)

[1] https://www.amazon.com/Native-American-Architecture-Peter-Na...

Winter: warm air comes in from the bottom vent, goes out from the top vent

Summer: cool air comes in from the top vent, goes out from the bottom vent

This dual inlet/outlet role from the same vent will have to be managed by some kind of valves/directer-plates inside the ducts.

a smart thermostat in every room

Vent open/close percentage controlled by each room's temperature (essentially vent acts like a per-room thermostat, while the main thermostat controls the overall/average temperature).

Disclaimer: I'm not an HVAC person.

I believe it comes in mini-split varieties but I did not choose that option as it was more expensive and I didn't like the aesthetics.

  * How much energy use? 
  * How much carbon do you want to burn?
  * How much money do you want to spend year over year? 
  * What kind of indoor air quality do you want to achieve?
  * What is your comfort zone temperature wise?

I don't know the scope of your project but consider getting a mechanical plan drawn up. Most residential projects don't have them and in my opinion (I've been building since 1999) it's a lost opportunity for a better, more efficient installation.

Something you should also do is make sure the place has really good insulation and windows/doors.

Or you can spend a lot more money and do what the top comment says.

Now that was a lame joke. But seriously you can find better answers in Reddit or other specialized communities.

In the PNW my todo wishlist is heat pump + zoned underfloor radiant + on demand gas boiler for supplementary heat and household water supply. TBD on cooling via ceiling/floor loops or separate wall mounted chiller/evaporator units.

I had gas fired boiler + radiant heat + supplementary resistive heating in each bedroom. I’m currently living with 3 zoned mini splits. Honestly happy enough with both, but structural radiant heat is just the best for comfort.

As a rule of thumb, as an Architect (the real one), I would start by using the best insulation you can afford. In a good percentage of inhabited places this will guarantee you a livable if not a confortable home. Then, according to your climate and economic environment (wood and derivates, gas, fuel, coal and electricity prices are highly variable depending of your specific location) invest in an heating source.

For cooling, multi-zone mini-splits are hard to beat. Per room control. Most of them are variable speed so they are exceptional at dehumidification in the summer. The heat pump capabilities on them are also tend to be significantly better than traditional HVAC systems. I've added them on to a few rooms and my garage; if I ever build another home or have to do a significant remodel/replacement of an HVAC system I will go with mini-splits. Also no ductwork in unconditioned spaces. If you do go with traditional HVAC and are going to have ductwork in traditionally unconditioned spaces like an attic, look at the recent trends in treating traditionally unconditioned spaces like attics/crawl spaces as condition spaces - there have been a lot of advances in insulation, ventilation, etc.

Finally as many others mentioned, if you are building a new home it should be a tight home (tight from air infiltration/leakage) so a heat recovery ventilator is a must.

An excellent YouTuber to peruse for lots of great ideas on how to improve on home building is Matt Risigner - I think he goes by The Build Show. There are lots of TV shows and people on YouTube pimping building advice but he's pretty approachable to even those not familiar with construction at all, and I haven't seen him hand out what I would consider off the wall or crazy advice - but he still will push the bounds of what is considered best practices in the industry.

Upgrading the right materials for your home can have a HUGE impact. A couple years back there was that major hurricane in Florida and there was the house that the homeowner spent about 20% more on and his survived, and all this neighbors for blocks were literally flattened. Even if you don't have major storms to worry about, well built homes are significantly more comfortable, healthier (I recently had a mold issue due to inadequate ventilation), and could even save you money on heating/cooling.