November 15, 2016

LUNOS Ventilation FAQ

lunos-e2-and-egoLunos HRV systems are a great way to add healthy, balanced and efficient ventilation to your project. For cold climate ventilation we offer three primary products: the Lunos e², Lunos eGO, and Lunos NEXXT. This post is mainly about the e² and eGO systems, each of which consists of through-wall paired fan units with regenerative heat recovery cores. These are the simplest – and often the most affordable – way of achieving continuous ventilation and good indoor air quality in airtight homes and multi-family residential units.

Q: Where do I start?
A: We offer many great technical resources on our website to help you specify, size, install and operate these systems. Start with the product pages and scroll through the tabs. Here are a few of the best:


Q: Where do I place Lunos e² fans?
A: An e² fan should go in every enclosed living space – including bedrooms, living room, playroom, home office, etc. Rooms that are located between synchronized pairs will also be vented from the back and forth air movement.


lunos-diagramQ: How is air transferred between rooms?
A: It is recommended to undercut interior doors a minimum of 3/4″ so that ventilation air can pass freely from room to room even if these doors are closed. If for acoustical or visual reasons doors cannot be undercut, air transfer devices should be integrated in walls or doors to allow for air to pass freely while reducing noise transfer between rooms.


Q: How many e² fans do I need?

A: First, remember that e² systems operate (and are sold) in pairs. Each pair delivers up to 22 CFM. There are several ways to determine the optimal number of e² fans. Rooms and apartments under 1000 SF might only need one e² pair. Small homes might need 2-3 pairs, or more depending on area, ceiling height and # of bedrooms.

  • Estimate: Measure the interior area (from drywall). A rough number is one e² pair for every 600-800 SF of living space.
  • Formula (from ASHRAE 62 2010):
    • Step 1: Divide the interior area by 100.
    • Step 2: Add 1 to # of bedrooms, then multiply by 7.5.
    • Step 3: Add Steps 1 & 2 for total CFM.
    • Step 4: Divide by 20 CFM to calculate number of fans
    • Example: 1,600 SF with 2 bedrooms = (1,600/100) + (3 x 7.5)  = 16 +  22.5 cf = 38.5 CFM  –> 2 e² pairs
      (See more examples here).

Modern Luxury Loft / Apartment by the seaQ: How high on the wall should the fans go?
A: Fans can go just about anywhere there is room, but it’s best to put them higher up on the wall to avoid being blocked by furniture. Also make sure to keep them at least 12″ away from ceilings and corners.

Q: Can I install fans in the ceiling?
A: No. Lunos e² and eGO fans can only be installed horizontally in walls (at a slight tilt to ensure outward drainage).

Q: Are these HRVs or ERVs?
A: Lunos systems in cold weather transfer 20-30% of the moisture back to the interior during each cycle. Since this is less than ducted ERVs which can transfer 50-60% moisture, we put them in the HRV category.

Q: How to choose between short and standard fans?
A: First, measure your wall thickness from the inside of the drywall to the outside of the cladding.

  • If your wall is greater than 10.5″, use standard fans
    (If between 10.5″ and 12″, cut tube no shorter than 12″ and box out your wall inward to make up the difference in thickness).
  • If your wall is less than 10.5″, use short fans
    (If less than 7.9″, cut tube no shorter than 7.9″ and box out your wall inward to make up the difference in thickness).

Q: How should I ventilate bathrooms?
A: For best practice we recommend installing a Lunos eGO in the bathroom for a fully balanced system with heat recovery. The eGO can be boosted to 12 CFM (balanced) or 27 CFM (exhaust-only) as needed.

Another common approach is to install a standard exhaust-only ceiling fan (or through-wall Lunos RA 15-60). Such a system is ideally on a timer or limited by a sensor to avoid unbalancing the building longer than needed.

Q: What about kitchens?
A: The Lunos eGO is a great way to maintain your kitchen IAQ 24-7, with the option to boost the CFM to remove odors. The eGO is often used in conjunction with recirculating range hoods for projects that want to avoid direct vent range hoods.

LUNOS-NexxtQ: Is the NEXXT right for my project?
A: First some background info. The Lunos NEXXT combines the advantages of centralized and decentralized ventilation for small to medium single family homes as well as multi-family projects. Unlike the Lunos e2 and eGO with their regenerative ceramic heat recovery cores, the NEXXT operates with a counterflow heat exchanger inside an attractive interior wall-mounted unit, with only one exterior penetration. It can be used either with or without ductwork, making it versatile for single or multi-room configurations. With up to two exhaust ducts, bathroom and kitchen exhaust can also be included. The NEXXT achieves a heat recovery rate of up to 89% with variable flow rate up to 60 CFM.

If you have a single large space, the un-ducted NEXXT is a simple and cost-effective option that can be installed right out of the box. If you have multiple rooms, the ducted option provides fully balanced operation for all of your spaces. Please call to discuss.

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