I'm looking for a HVAC system or device which can maintain predefined air temperature, humidity and CO2 level in the house. It would be nice if such a system can be upgraded to scale it for more rooms/zones with independent sensors in each zone. Both commercially available systems and custom projects are considered.

UPD: Some clarification is really needed:

  1. I want such a system for a normal residental house.
  2. Humidity control is important during winter, usually it is hard to get 20% in-door humidity without extra device.
  3. High concentration of CO2 level is not really healthy for people, and I'd like to keep it lower than that. The idea is increase ventilation flowrate when CO2 level rises.
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    Why & how would you maintain a set CO2 level? Is this for a greenhouse or something specialized? – Xen2050 Mar 4 '19 at 8:59
  • Hello, and welcome to Home Improvement. Controlling CO2 levels is probably off-topic here, but more details would help us know (and perhaps help you). – Daniel Griscom Mar 4 '19 at 13:36
  • No, for a regular residental house. CO2 level above 800 ppm is not healhy for people, it would be nice to maintain it below all the time. – zeliboba Mar 4 '19 at 13:40
  • All HVAC systems primarily maintain temperature. Many (via humidifier for heat use) also maintain humidity. However, CO2 is not "maintained". If a system burns stuff (oil, gas, etc.) then ideally all gaseous combustion products (primarily CO2) are vented to the outside. If a system is electric or geothermal or a heat pump then there is no CO2 produced. But the system can't (unless you are talking about million dollar NASA systems, etc.) actually adjust the CO2 level per se. – manassehkatz-Moving 2 Codidact Mar 4 '19 at 15:18
  • Has someone been inspired by Tom Scott and Kurtis Baute? youtube.com/watch?v=1Nh_vxpycEA – longneck Mar 4 '19 at 16:01

A humidifier is required to increase humidity. They come with a humidistat or you can use some smart thermostats to control them.

Running the fan/furnace will not clear any accumulated CO2 or other molecular indoor pollutants. You would need to exhaust air from your house and bring in fresh air.

Normally you don't need to concern yourself with CO2 unless your house is extremely tight(r2000) . Most houses built to that standard are already equipped with one of the following; an HRV (heat recovery ventilator) or for southern climates an ERV (energy recovery ventilator). There are options for control ranging from manual to timed or continuous with boost. I'm not familiar with CO2 monitoring to bring it on.

So basically for heat you need a furnace, (which you have) For humidity you need to add a humidifier and to maintain safe air quality you need an HRV or ERV depending on your climate.

** Dedicate HRV**enter image description herewww.finehomebuilding.com

** Integrated HRV**enter image description herewww.skepticrant.com

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  • Comment on the question specifically states they want to maintain a low, healthy CO2 level. – JPhi1618 Mar 4 '19 at 16:06
  • Oh shoot missed that. In that case fresh air through a heat recovery ventilator (HRV) would be the best option – Joe Fala Mar 4 '19 at 16:36
  • Certainly I'm looking for a solution wich takes air from outside, warm it up and moistirize it depending on temperature and himidity level in the house. The reason for having an additional CO2 control is pretty simple: I observed that CO2 level increased significantly when use gas oven for cooking, and I'd like to take this into account to control air ventilation flowrate. That's true, I did not see CO2 measurement in commercial systems, but I've heard about DIY projects, and I consider them also. – zeliboba Mar 6 '19 at 15:17
  • You could install a dedicated HRV/ERV system to exhaust air from your kitchen can bring in fresh air from outside it's a fairly involving procedure but is common. The yard bulky and require for pipes to be hooked up and thus take up quite a bit of space. I'll add a photo in my answer. – Joe Fala Mar 6 '19 at 15:30

The normal way carbon dioxide is regulated is to add a makeup air intake on the furnace. With todays homes being sealed I believe this should be a mandatory part of an HVAC system. An automated system could be added that would open a damper at a preset level but this would be expensive. I usually size the makeup air port based on the size of the home and how many people live there. Every time you exhale approximately 5% is Co2 so the number of people in the home makes a difference. I will usually double the size make up air damper and close it to 50% this way if the home owner wants more fresh air pumped in they can open the damper further. Remember that this will increase heating or cooling costs as conditioned air is being pushed out of the home, usually through the kitchen, bath and dryer vents. With older water heaters and gas furnaces make up air also helps them to vent better because of the positive pressure greatly reducing the chance of carbon monoxide leakage in the home.

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