Cooling a home theater

Media rooms are unusual among the rooms people ask us about, because the normal escape hatch is closed. In a bedroom, a garage or a home office you can always turn a fan up. Here, anything you can hear during a quiet scene has failed.

Before buying anything, work out what you are fighting. Media rooms have an unusual heat profile: relatively little from the fabric of the building, and a great deal from equipment and people.

• The projector, if you have one, is usually the single largest source and it is on for the whole session. Check its manufacturer specification for input power — whatever it draws becomes heat in the room, near enough entirely.
• The amplifier or AV receiver, particularly a class-AB power amplifier driving several channels. Much of what it draws does not become sound.
• Source equipment and games consoles, which are small individually and add up in a closed cabinet.
• The people. A seated adult is a continuous heat source, and this is a room designed to hold several of them close together.
• Very little from windows, unusually — a media room is normally blacked out, which removes the solar gain that dominates most rooms.

That profile matters because it means the load is steady and internal rather than peaking with the afternoon sun. Cooling that is sized for a sunny bedroom will behave differently here.

This is the central idea and it solves most of the conflict.

A sealed, blacked-out room with a closed door is well insulated against the outdoors almost by accident. That means it holds a temperature for considerably longer than a normal room does, which in turn means the compressor does not have to run while you are watching.

1. Pre-cool for 30 to 60 minutes before the session, harder than you would normally set it. Two or three degrees below target gives you headroom.
2. Switch the compressor off as the film starts. A timer, an app or simply a habit.
3. Leave continuous low-speed air movement running. A ceiling fan at 1 to 3 W is inaudible and keeps the room from stratifying, which is what makes a still room feel stuffy.
4. Run the compressor again in the interval, or between episodes.

The equipment rack is the exception and should run continuously, because electronics do not get a break during the film — and heat soak in a closed cabinet is what shortens their life.

A closed AV cabinet with a receiver in it is a small oven. It is also the easiest thing on this page to fix well, because you are moving a small volume of air rather than conditioning a room.

In rough order of effort:

• Open the back of the cabinet. Free, and it is frequently enough on its own.
• Add a vent at the top and another at the bottom. Warm air leaves the top, cool air is drawn in at the bottom, with no fan at all. Convection is silent by definition.
• Add a small continuous fan, running slowly all the time, rather than a large one running intermittently. Continuous and slow is both quieter and better for the electronics.
• Duct it out of the room with an in-line fan, which is the proper solution and the only one that removes the heat rather than relocating it — the same principle applied to a server closet.

We have to be straight about this, because it is the specification you most want and the one least reliably published.

Ceiling fans publish no noise rating at all. The ENERGY STAR certified dataset covers airflow, wattage at each speed and standby power, and contains no sones or dBA field. Nobody has a certified noise figure for a ceiling fan, including us.

What we can use is a reliable proxy: a fan that achieves high airflow per watt can deliver useful air at a low speed, and blade noise scales sharply with tip speed. A 366.7 CFM-per-watt fan on its lowest setting is doing what a 189 CFM-per-watt fan needs a higher speed to do.

Portable fan dBA figures exist but are manufacturer-measured under conditions that vary, so they are comparable within a brand and unreliable across brands — what fan noise figures mean and the quietest fans we can evidence.

If your media room is below grade, you probably have a humidity problem as well as a heat problem, and it is the more damaging of the two.

A basement stays cool, which is good for the equipment, but cool air holds less moisture before it condenses. Electronics, screens, seating and acoustic treatment all suffer in sustained high humidity, and speaker surrounds in particular do not enjoy it.

A dehumidifier is doing a different job from an air conditioner here, and in a cool basement it is usually the right machine — basement dehumidifiers and cooling a basement generally. Bear in mind it adds a little heat and its own noise, so put it on a humidistat and let it run when the room is empty.