Can You Heat and Cool Your Home with the Power of a Hair Dryer?

We say you can heat and cool a passive house with the power of a hair dryer. That’s a real claim, not a marketing slogan, but it deserves some explanation because it can’t happen with every home we build.

The Number Behind the Claim

A standard hair dryer runs on about 1,500 watts. In August, 2025 we measured the electrical load of the heat pump AC as it cooled a 2,600-square-foot passive-level home we built near Kingston Springs, Tennessee. Outside temperature: 100°F. Inside temperature: 70°F. Total energy consumption: approximately 1,300 watts.

We’re not going to tell you that works for a 5,000-square-foot home. It doesn’t scale linearly, and we won’t pretend otherwise. What we will tell you is that the underlying principle holds across the homes we build, because the principle isn’t a slogan, it’s math.

We Don’t Use Rules of Thumb

The standard approach in Tennessee HVAC sizing is roughly 1 ton of cooling per 500 square feet. For a 2,000-square-foot home, that means 4 tons of cooling capacity, a system sized for a building that leaks air, absorbs heat through poorly insulated walls, and fights humidity it was never designed to control.

We don’t use that rule of thumb. On every home we build, we perform full Manual J, S, and D calculations, the engineering methodology for calculating actual heating and cooling loads based on the specific building, its orientation, draftiness, insulation levels, window performance, and the local climate. If the client wants them and the budget allows, we also run full energy models using WUFI Passive and/or PHPP, the same software used to certify passive house projects worldwide.

The result: on a well-built 2,000-square-foot passive home in Tennessee, we’re typically sizing around 1 ton of cooling. Not because we’re cutting corners, because the building doesn’t need more than that.

The System We Actually Install

Smaller doesn’t mean simpler. A passive house HVAC system has three distinct jobs that a conventional system handles poorly or ignores entirely:

Temperature control is handled by a cold-climate heat pump, sized to the actual calculated load, not a rule of thumb.

Humidity control is handled by a dedicated dehumidifier, separate from the cooling system. In Tennessee’s climate, humidity is often the bigger comfort problem, and a heat pump running in cooling mode is a mediocre dehumidifier at best. And in the spring and fall, the outside temperature is pleasant, meaning the AC doesn’t run even though the air is still humid. We treat humidity control as its own system because it is.

Fresh air is handled by an energy recovery ventilator (ERV), which continuously exhausts stale indoor air and brings in filtered fresh air from outside. The ERV recovers most of the energy from the outgoing air stream before it leaves the building, so you’re not throwing away conditioned air.

These three systems work together. None of them recirculates stale indoor air which is how most conventional systems operate, filtering the same air over and over while humidity and pollutants gradually accumulate.

What This Means for Indoor Air Quality

Mold requires moisture. Allergens accumulate in humid, poorly ventilated spaces. Dust mites thrive above 50% relative humidity. But when you stop recirculating stale air and start managing humidity as its own variable, something changes in the indoor environment.

A passive house running a dedicated dehumidifier and a continuous ERV maintains lower humidity, continuous fresh air, and better filtration than a code-built home running a conventional system. The occupants notice, particularly those with allergies or asthma. This isn’t incidental, it’s designed in from the start.

The Honest Version of the Claim

So, can you heat and cool your home with the power of a hair dryer? If you build a reasonably sized home to the passive house standard, size your systems with real engineering calculations, and design the home to work with your climate rather than against it, then yes, you can get remarkably close. We have the data from a real home in Tennessee to show it.

If you want to talk about what that looks like for your project specifically, contact us here or call (615) 898-9115. We’ll run the numbers.