May 5, 2016

Ventilation’s Energy Problem: Most Of It Just Sucks

Inaugural post of the Turning BS into Building Science series by Lucas Johnson

Most often, ventilation sucks.

When I was the third contractor enrolled in Energy Upgrade CA, I enjoyed being on the cutting edge of high performance building. However, ventilation was repeatedly one of the biggest challenges we faced as a state trying to push for affordable deep green buildings.

Then I moved to Seattle and became the in-house building scientist for Community Power Works. We retrofitted over 3,000 homes as well as hundreds of businesses ranging from mom-and-pops to CenturyLink Field. Again, ventilation plagued our work, resulting in wasted energy, unhealthy conditions, and maintenance headaches.

Here’s why ventilation sucks.

The large majority of ventilation systems for smaller buildings are exhaust-only and run continuously or intermittently. In other words, they suck air out of a given room, most likely the bathroom, and then we basically just hope that the make-up air isn’t toxic or moisture-laden.

What we do know is that the best-case scenario is the make-up air is pulled directly from outside. Opening a window is the easiest way to make sure this happens, but that means pulling in 100% outside air that needs to be heated or air conditioned. A huge waste of energy!


Furthermore, if the bathroom window is open the bathroom fan will never work as your “whole-house” solution. Using the 2 cfm for each square inch rule, it only takes 40 square inches to allow 80 CFM to be pulled into the bathroom directly from outside. This means that opening a standard 30” bathroom window by only 1.33” would make it so that the bathroom fan is only pulling make-up air directly from outside which means NOT pulling air from anywhere else in the house.

Or, even more likely, the bathroom has the equivalent leakage area of almost 40 inches due to gaps such as the P-trap for the tub, the holes cut for the plumbing, electrical outlets, and the rough cut around the bath fan.

So how can we change home ventilation so that it stops sucking? By making it balanced. Even better, specifying a balanced ventilation system with heat recovery.

Balanced, Decentralized, Adaptable, Heat Recovery

Especially for tightly built and efficient homes, the most simple and cost-effective way to deliver balanced heat recovery ventilation is by using through-wall ventilation, because there is no ducting. The LUNOS e2 and LUNOS eGO work together as a modular system to create balanced heat recovery ventilation. Central HRV systems can work well; however, they are more expensive, the ductwork is always challenging, the central units require a large closet space, and the fan energy use can be significant for any central system.

The brilliance of the system is the simplicity. Sizing a LUNOS system is as easy as calculating the total CFM required based on square footage and occupancy, then adding units based on that calculation. Read our extended description on sizing LUNOS e² through-wall ventilation units. One eGO unit goes in each bathroom, providing continuous ventilation with heat recovery, and the option of exhaust ventilation when needed.

LUNOS systems are working now throughout North America. From Los Angeles to Maine to an off-shore Alaskan oil rig (seriously), they’re being used for efficient ventilation for projects shooting for net-zero-energy levels of efficiency – they only draw about as much energy as an LED bulb. They’ve been installed and tested, with no freezing or defrosting, and have become the favorite ventilation system for off-grid cabins and tiny house enthusiasts across the country (see here, here, here, here, herehere, here … you get the idea). It’s also a great solution for multi-family projects, because you can completely separate spaces, without mixing of air between units.

Want to know more about why most ventilation sucks? Questions about how LUNOS can fit into your building project? Contact us to learn how we make high performance ventilation simple, affordable, and effective.

Lucas Johnson is the West Coast Solutions Consultant for 475 High Performance Building Supply

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7 Responses to Ventilation’s Energy Problem: Most Of It Just Sucks

  1. James Maher May 17, 2016 at 8:53 am #

    What solution would you recommend for kitchens?

    • John May 17, 2016 at 10:31 am #

      We recommend using a recirculating range hood in the kitchen. As with any building that has continuous ventilation with heat recovery, ideally you don’t want the extra hole to the exterior. If you do choose to use a traditional vent to the exterior, it drops the efficiency of the overall heat recovery system. The greater the airtightness, the less heat loss from infiltration. Traditional ventilation without heat recovery throws off the balance of the system while they are operating as well. The continuous low-flow ventilation will dissipate any cooking smoke or odors, so locating a Lunos unit near the kitchen is a good idea. It won’t suck all the air out of the house at once, like a 350 CFM range hood would. But that is the point – your energy leaves the building along with the air. Hope that helps.

  2. Barbara Smith May 19, 2016 at 11:11 am #

    Traditional whole-house ventilation systems pull stale Air from bathrooms and the kitchen and supply fresh air to the living areas and bathrooms. It seems like you’d need a unit for every room in the house to supply fresh air to the living areas and bedrooms.

  3. Gordon October 21, 2016 at 9:12 am #

    Would the eGo work if installed vertically rather than horizontally, as long as the exterior is protected from rain? I would like to install one for a travel trailer. Replacing the existing bathroom ceiling exhaust fan with the eGo would avoid the need to create a new hole through the wall, and power is already wired to the opening.

    • John October 21, 2016 at 4:26 pm #

      Hello Gordon,

      Unfortunately no. All Lunos products are made to operate with a slight pitch to the exterior. Firstly to stop rain intrusion, but even if it were possible to prevent all rain, condensation will still occur as part of regular operation, which needs to drip to the exterior, hence the slight pitch outward. Although it would make a great replacement for that exhaust fan, it would have to go in a new hole in the wall. Let us know if there’s anything else we can help with.

  4. Steve Keene November 4, 2016 at 7:42 pm #

    Interesting idea. Can you extend ‘tube’ by adding duct to pass through knee wall voids to outside. We have a bonus room above garage and would like to place one on each knee wall at opposites but need to pass through the void to get to the outside. Likely through soffit overhang. Worried about dripping condensate and pulling in ‘fresh’ air with all the dust and fiberglass if installed using the standard tube length that would end in void itself. Room is finished and adding them to the gabled ends would be a bear trying to get them wire. Thoughts? Thanks.

    • John November 8, 2016 at 12:07 pm #

      Steve, ducting is not allowed with the Lunos e2 and eGO units. The maximum the tube can go is the extension tube available on the site: 27″. The Lunos Nexxt, however, is capable of ducting. Please contact the office to discuss ducting possibilities and send us a detailed drawing of your wall, if possible. We should be able to help you.

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