I am designing a computer room inside my home. The room walls are inside the house. This question excludes floor, wall, and ceiling losses/gains.
I am looking for the formula to calculate the CFM required to keep the room interior temperature close to the exterior temperature.
I have been using this formula:
hs = 1.08 q dt
- hs = sensible heat (Btu/hr)
- q = air volume flow (cfm, cubic feet per minute)
- dt = temperature difference (oF)
- 1.08 = the heating BTU multiplier at sea level, or .075-lbs. of air per CFM x .24 (the specific heat of air) x 60 (minutes in an hour.) This factor will vary at higher altitudes and temperatures.
6,800 BTUs of heat generated in a 12x14x8 (1344 cubic feet) room. The incoming air temperature is 72 degrees. The target room temperature is 78 degrees.
q = hs / (1.08 dt) = 6800 / (1.08 x 6) = 1079 CFM.
- Is this formula correct or is there a more appropriate formula?
- What is the formula for heat rise in case the ventilation system fails or the CFM degrades?
Note: I am not looking for rules of thumb. The room does have a mini split, but during the winter I want to ventilate the heat into my home and not condition the heat. During the winter the mini split is part of my ventilation failure cooling plan. The failure plan includes a temperature alarm that shuts down the UPS system which shuts down the computers.
For those that are also thinking about a dedicated computer room at home:
- The room is 12 x 14 with 8-foot ceilings.
- The room has a dedicated subpanel with an outside generator hookup.
- 3,000 Watt APC Smart UPS
- Supports 2,000 watts of computer equipment.
- Dual gigabit Internet providers connected to a bonded router.
- 12,000 BTU mini split air conditioner with low-temperature cooling support (wine room).
- Temperature alarm shuts down UPS which shuts down the computers.
- Plumbed for water and drainage.
- In-wall dehumidifier.
- In-wall humidifier.
- Medify Air Purifier.
- Incoming air: MERV 13 4-inch filter.
- Two temperature-controlled variable speed 10-inch duct fans to exhaust heat during the heating season. Only one is required, two provide redundancy. Shutdown during the cooling season. Mini split ensures a temperature ceiling. If the mini split turns on the fans turn off (current sensing relay).
Google now recommends setting data center temperature to 80 degrees. This recommendation works with my goal of exhausting air into the house during the heating season. [link]
The purpose of this question is to calculate the CFM required to exchange the air in the computer room to maintain a reasonable temperature and take advantage of the heat generated during the heating season. During the cooling season the ducts are closed and the mini split provides for conditioned air. The MERV 13 filter ensures clean air in the computer room during heating season. A standalone air filter provides air quality during the cooling season.
There are additional construction details to support a low-cost conversion to a wine room to make a home sale easier in the future. My comments under the accepted answer provide some of those details such as R-19 insulation in the walls and ceiling, exterior grade insulated glass interior door, etc.