If you have a gas fired boiler and hot water heater then you have to make sure the mechanical room has enough air for combustion. The appliances themselves are efficient and well insulated so they should not be heating up the room.

It might be possible to provide enough combustion air from the house by installing a louvered door to the room. Whatever you do the HVAC installer needs to do a calculation based on the amount of gas you will be burning and the air exchanges of the house. You may need to install a HRV if the volume of air surrounding the mechanical room is not sufficient.

I've not seen a boiler that required house supplied combustion air in many years - all are sealed combustion. Similarly, most houses that have boilers also have side arm domestic water heaters (water from boiler is used to heat domestic water) so no gas nor combustion air involved.

You've got a couple of different issues.

A problem with waste heat implies thermally-inefficient equipment. Investing in higher-efficiency equipment will help to minimize the both the amount of, and cost of energy wasted.

If you need to provide combustion air to combustion devices, consider sealed combustion units; they'll have ducted exterior air supplies and won't consume (conditioned) room air as combustion air.

HRV's are typically part of a strategy for maintaining indoor air quality when building a "tight" home. They bring in fresh air and recuperate heat from the exhausted air. They are not the best solution for reducing the temperature of a hot mechanical equipment room.

Thanks for your comments .. so the appliance we are thinking of getting is the https://www.navieninc.com/series/nfc - no concerns about air coming in from ourside it has in/out vents which are sealed.

It's pretty energy efficient. But the room will also house my home server which will have fans giving off heat as well as modem/internet hardware + amp for the home theatre - they are far away from the combi, I don't have a concern with water damaging the electronics, but I'm 90% the room will get warm.

So I'm trying to "cool" the room but I don't want to waste the heat which is being generated (and i'm kind of paying for) by exhausted out. The house is going to be pretty air tight < 2 ach, so I don't want a vent to the outside ruining all the hardwork done trying to be energy efficient.

Hence my thinking I could "capture" the heat in the HRV exchanger (which would then help pre-heat the incoming cooler air for the house) - hope all that makes sense.

Thank you

A mechanical room is an appropriate space to locate HVAC equipment and hydronic equipment. It's not appropriate for electronic equipment in my opinion. I suggest you subdivide the space into two separate spaces and condition the electronic equipment room.

Since you intend to build a "tight" home, I encourage you discuss options for whole house ventilation with your contractor. Here's a link to some basic information to start with:

https://www.energy.gov/energysaver/weatherize/ventilation/whole-house-ventilation

You need to understand the operating temp recommendations for your electronics. Most are good up to at least 104°f. Make sure you allow proper spacing between devices and have proper cooling in your racks (which is not just fans if necessary but making sure that each piece of equipment has proper airflow). Most mechanical rooms should not become too hot. If you want an extra measure of safety then pull air from your house (usually hallway adjacent to mechanical room) in to your equip racks.

@Charles Ross Homes is correct that ideally electronics should not be in the mechanical room but sometimes practicality says otherwise. And enclosing a space within the mechanical room without specific cooling for it can lead to worse heat problems so quite often placing electronics in an open mechanical room where ambient cooling can happen is the best option.

Off the top of my head we'll have two equip racks in our mechanical room for electronics including;

- Fiber modem

- Fiber mux

- Netgate XG-7100

- Ubiquity Switch Pro 48

- Ubiquity Switch Pro 24

- Ubiquity Cloudkey

- Synology RS3617xs+

- 2 Synology expansion units (Total of 82tb of server storage)

- NVR (model undecided)

- 4 Anthem Amps (models still undecided)

- Control 4 system

- Regulated power supply

- UPS

- Other stuff that I can't remember right now.

We don't expect any problems.

If mechanical room has enough volume, consider a heat pump water heater instead of tankless unit. It's likely to be cheaper to operate and provides cool, dehumidified air to help address the equipment heating.

HRV setups don't provide a lot of CFM. Better to use that limited resource on providing fresh air to living areas and bedrooms while exhausting from the known pollution sources of kitchens and bathrooms though there may be IAQ concerns with the electronic equipment too.

Agree that dedicated heating and cooling equipment is a better strategy but sounds like you are in a heating dominated climate. A heat pump water heater could be a more affordable way to heat water while addressing the extra heat from the electronics. I might even go HPWH below suggested room volume if expecting a lot of heat there. It's a good opportunity for mechanical symbiosis.

"A mechanical room is an appropriate space to locate HVAC equipment and hydronic equipment. It's not appropriate for electronic equipment in my opinion. I suggest you subdivide the space into two separate spaces and condition the electronic equipment room."

+1

Be sure to ventilate the electronics room. Heat is the enemy of electronic devices

If this were my building project, I would put all HVAC and water heating equipment in one enclosed but large enough space so that the equipment is easily accessible and not on top of one another. Provide that space with makeup air and ventilation as required by code and good practice. Build it with the same techniques as an attached garage - close off air leakage to the main house (wall protrusions, power sockets,etc) and have weatherstripping around the door as if it were an exterior door.

With adequate supply of makeup air, it won't need further ventilation.

@opaone - we are going to end up with similar amount and type of equipment (I've not told the wife but my plan is use put in a server rack). The room is 8 x 13 and 8ft height, so med sized?

The combi shouldn't give off too much heat but it would be nice to capture any heat in the room. @Springtime Builders I did look into these tanks which have a air source heat pump - neat idea. But we have a potential power issue. We are more or less tapping out our total amps available for the house (200), to get the next 200, it's 35-40k :(

The storage tanks I've seen (RHEEM) have the air source pump sitting on top but still use electricity to heat the water .. and I don't think we have the spare amps. Unless there was something that didn't use an electrical element in the tank but exclusively used the heat in the air to heat the water... but I don't know if something like this exists. I've not found it.

We are based in Vancouver, Canada. Thanks for any further ideas on this issue. Ideally the electrical equipment would be elsewhere but space/limits etc and it IS called the mechanical room it seems like the right place to put all this. In theory there shouldn't be any water in this room as such (unless things go wrong - and it's a new build so that should happen)