Sizing Lunos E2 through-wall ventilation units

Exploded View of E2

475 is excited to be offering the Lunos E2 to the US marketplace – a new ventilation option of extraordinary value.   The value is from very high heat recovery efficiency – providing not just monetary savings but comfort, ease of installation and the elimination of a ducted distribution system.

Installed in pairs, the E2 can provide a unique high-performance solution for retrofit and new homes of modest size.    Modest sizing because the volume of air a pair provide at any one time is limited to 9, 18 and 22 cfm – a small amount by any standard. But a large improvement when compared to ventilating houses through a leaky enclosure or counting on the windows to be opened to get the required fresh air in.

We use ASHRAE 62.2 as our guideline to determine minimum acceptable sizing for general living/bedroom area ventilation.  (See notes below for bathroom and kitchen ventilation.)

Per ASHRAE 62.2 total cfm required = 7.5cfm/occupant + 1cfm/100sf.   (Occupant number is determined by the number of bedrooms + one.)

For the output of a Lunos pair we use the medium setting of 18cfm/pair.  Let’s illustrate using a few common rough home size/configurations:

Apartment Plan Diagram

• 500 sf studio = 7.5cfm*1 + 500/100 = 12.5 cfm min. = One pair
• 700 sf one bedroom  = 7.5cfm*2+700/100= 22 cfm min. = Two pair.
• 1,000 sf two bedroom = 7.5cfm*3+1,000/100= 32 cfm min. = Two pair.
• 1,500 sf three bedroom = 7.5cfm*4+1,500/100 = 45 cfm = Three pair.
• 2,000 sf four bedroom = 7.5cfm*5+2,000/100= 57.5 cfm min. = Four pair.

From the above outline we can see that as the home moves from a modest to larger size the number of pairs increases significantly.

At kitchens and bathrooms per ASHRAE 62.2, we recommend installing intermittent exhaust fans.  The exhaust fans should have timers, motion sensors or switches to limit their use and their impact on the ventilation efficiency.

With this setup one may not be able to achieve Certified Passive House levels, yet given an airtight enclosure, one can have a very efficient, comfortable and healthy home.

US Army Corp of Engineers – Passive House Workshop Event

March 6-8, 475 is looking forward to attending a series of workshops about high-performance enclosures in San Antonio, Texas.   The workshop is a collaboration between the US Army Corps of Engineers (USACE) and the Passive House Institute (PHI).

The Army, Navy, Air Force, General Services Administration and the Department of Energy and other private sector contractors will be participating.

The workshop is geared toward architects, engineers, project managers and contractors and will address topics relevant to new construction and deep energy retrofits.

As part of the event Berthold Kaufmann of PHI, and Tomas O’leary of the Passive House Academy (PHA) will make a series of presentations on Passive House construction.  Floris Keverling Buisman of 475 will be there too.   Be sure to meetup with Floris with an email to floris@foursevenfive.com.

To register for the workshop, contact:

Lyndsey N. D. Pruitt, LEED AP BD+C
USACE HQ Engineering & Construction
Sustainability, Energy, Architecture
W. 202.761.8900
C. 202.701.0281
Lyndsey.N.D.Pruitt@USACE.Army.Mil

We hope you can make it!

Intentional “holes” in your air barrier (and sealing them)

The red line that many of us draw on the interior of our insulation to indicate the continuous airtight layer that provides comfort, optimizes the insulation and keeps it free from condensate and mold – has to be punctured at least a few times to get life necessities into the Passivhaus (water, air, electric, sewer, telecom) – so we need to seal at a minimum around the following:

•  2 ducts for HRV (supply and exhaust)
•  1 electric conduit which carries 3 cables
•  1 potable water supply pipe
•  1 sewer connection
•  1 cable/telephone wire

Kaflex gaskets are great, but always try to minimize the number of cables first (image: http://blog.proclima.com)

Although these leaks mostly do not appear on that red-line section you made, you should plan your connections to these ‘holes’ so they will be sealed properly and will remain airtight for the live of the building – which is the topic of this post – Of course, reducing the holes you have to a minimum is the first step, as it lessen the number of seals you need to make and worry about for getting to Passive House 0.6ACH50. Hence the use of service cavities to prevent unnecessary penetrations of your red line.

Only one cable per hole please

 

Recommendation number 1:

Only one pipe, cable, wire or duct per hole.

The reasoning behind this is that foam won’t expand it in the way you want it too, so it will not give you an airtight seal between the small spaces in-between the cables/pipes. This is explained quite well by Roger Lin at the bottom of this blog post of the Arlington Passive House. Furthermore shrinkage of the foam or movement of the cables will compromise foam-cable connection and thus compromise the seal. KAFLEX and ROFLEX EPDM gaskets are the preferred way to seal cables. (Note: sealing Romex will be subject of a future blog post)

Foaming many pipes and cables in one hole - looks airtight, but will still leak air (http://arlingtonpassivehouse.wordpress.com)

Recommendation number 2: Give your self space to make a good airseal.

Good amount of space to fit HRV ducts, apply insulation around them and plachttp://passivhausrefurb.blogspot.com/)e + tape ROFLEX gaskets (

You need at least a few inches around a larger duct to place your hand and press the tape securely to the membrane (see photo on the right). For smaller pipes and cables, you can work with smaller tolerances, but don’t make the job harder than it should be – it is just not worth it. The picture below shows a situation in which the conduit is already installed and a gasket can be slid over it. It will be practically impossible to get a 100% seal because of the different levels of wood surrounding it.

Recommendation 3:

Distribute gaskets early to plumbers/electrician so they get used

conduit to close to stud to make a proper sealed air-tight connection (vermontpassive.com)

Using TESCON No.1 in short strips to connect pipe to airtight layer

If you install gaskets over pipes and cables during installation, they remain adjustable and the connection/taping to the airtight layer can happen at a later date.Making the process quick, airtight and easy for all involved.

Yes, of course you can tape around pipes with a large amount of short strips of TESCON No.1 as shown on the right. This takes more time, is more prone to mistakes that cause small airleaks and won’t allow you to adjust the pipe anymore. However, it the pipes/cables are already installed this would be your only option, just be diligent and make the best seal you can.

Recommendation 4: No new holes!

This pipe and hangers were installed very late in a PH project and thus all of them needed to be taped with Tescon No.1, with some planning this could have been prevented

There is a chance that you will show up on site and find some new holes in the airtight layer – new plumbing pipes, extra exterior lights, cat-doors, sewer vents, etc. Either were installed late or weren’t on the plans but that the owner really wanted them and told the contractor to install. Recommended is to explain the importance and comfort that air-tightness will bring the owners (and contractor), have them witness a blowerdoor-test early on, which will hopefully mitigate these unannounced arrival of these new holes

(during construction and during the life of the building – a dedicate service entrance could be a remedy for utility and cable companies to counter their leaking service installations – however, you still need to watch them….).

Better Buildings and many more of them

McGraw Hill Construction

McGraw Hill has just released key findings of a new study/survey to be published in April, showing that while residential construction has collapsed over the last several years, green construction has been steadily growing – gaining significant market share in the process, and totaling approximately 17%, or $17 billion in 2011.  McGraw Hill estimates that as residential construction rebounds, the green market growth with accelerate, exceeding a 30% share or $100 billion by 2016 – a five fold increase in five years.

For evidence of this green explosion one needed only to attend last week’s Better Buildings by Design Conference in Burlington Vermont.   Produced by Efficiency Vermont, this “little” conference packed a punch – with informative and wide ranging talks on building science and efficiency, from luminaries such as John Straube of Building Science Corp and Bill Maclay of Maclay Architects, as well technical talks on ventilation by Barry Stephens of Zehnder America and data collection by Peter Schneider of Efficiency Vermont - to name just a very few.

Better Buildings by Design

And the exhibitor floor was packed with important players in the green building world from National Fiber to Preferred Building Systems.   But perhaps the most important aspect of the conference were the attendees – a cross section of professionals committed to building more efficient, comfortable and healthy buildings.  Contractors, architects, college professors, developers and specialists, made for two days of interesting and intense conversation that was impressive and inspiring.   475 was very happy to be there as an exhibitor and to meet so many dedicated people.  We look forward to being back in 2013, and encourage you to be there too.

To many, many more better (green) buildings.

Air & Vapor, Part 2: The Importance of Air Tightness

In Part 1 of Air & Vapor we started our discussion noting the importance of air tightness and vapor control in building enclosures, as second only to keeping the rain out.

Control Layer Priorities:

1. a rain control layer
2. an air control layer
3. a vapor control layer
4. a thermal control layer

In this post we’ll discuss the importance of air tightness.

Air control at the enclosure is so important (two notches above insulation) because it has profound effects on:

1. Indoor Air Quality (IAQ)
2. The optimization of thermal insulation
3. Prevention of bulk vapor penetration.

For these reasons, air control and air tightness is a cornerstone attribute of any high-performance building, including  Passive House (Passivhaus) buildings.  So let’s take a closer look at the power of air sealing and air tightness:

Indoor Air Quality (IAQ)

You can’t control the quality of the air we breathe until we control it physically.   Unfortunately this is a widely ignored fundamental truth.   Until we control the air flow through a home the IAQ is a crapshoot.    And the first step in controlling the air flow in a building is an airtight enclosure with a continuous air barrier.

Ventilation fresh air filter, full of exterior soot, pollen and other contaminants

Once an airtight enclosure is established, the air inside can be controlled predictably and efficiently.   High IAQ becomes not only possible but simple to achieve.   Fresh air can be brought in continuously with stale air exhausted continuously.    The fresh air is filtered as it enters the home, removing soot, pollen and other pollutants and supplied to living areas.   Exhaust air is taken from bathrooms and kitchens and brought through a high efficiency heat exchanger, swapping its energy to the incoming fresh air before it is expelled to the outside.

In this way – made possible with an airtight enclosure – air quality inside the home may be superior to the outdoor air quality.

Optimization of Insulation

Air leaks through the enclosure can severely compromise the effectiveness of the thermal control layer.  A study by the Fraunhofer Institute for Building Physics, in Stuttgart, showed that a leaky enclosure can decrease the insulation’s effectiveness by a factor of 4.8 – making a 500 sf leaky building require the same amount of heating as a 2,400 sf airtight building!

Diagram of insulation unprotected by air tightness (at left) and protected by air tightness (at right).

Consider your sweater on a breezy day, and the effect of putting on a windbreaker.

The insulation performance is best optimized with an air-tight layer on all sides: an air-tight layer at its interior face (such as Intello Plus) and a wind-tight/air-tight layer on the exterior face (such as Solitex Mento).

If you are going to bother to insulate, get the most out of it with with complete air sealing and airtightness.

Prevention of Bulk Vapor Penetration

BSC: diffusion wetting vs. air leak wetting.

While there is much gnashing of the teeth (and some of it rightly so) about vapor diffusion resulting in condensation and structural damage, a far bigger threat to the structure is bulk water vapor penetration via air leaks in well insulated buildings.

With this iconic diagram from the Building Science Corporation paper RR-0412: Insulations, Sheathings and Vapor Retarders, one can see that the potential water intrusion from just a small air leak can be up to 90 times greater than the water that might diffuse through gypsum board into the enclosure.

With such extreme wetting, even a vapor open construction may not be able to dry fast enough to keep the structure safe.   Here we see water damage from an air leak in a such a vapor open construction.

Water damage from air leaks in vapor open construction.

Uncontrolled air movement through OR within* the building enclosure, carrying bulk vapor, causes the greatest amount of moisture related building damage.  Keeping the enclosure airtight on the interior is an essential step in keeping it dry.

*convective loops within wall cavities can transport and deposit bulk vapor when it reaches the dew point.

Conclusion

Because air tightness is essential for clean indoor air, optimized insulation and minimizing of wetting damage, it should be seen as a fundamental and integrated insurance policy on the performance of the building.   The more airtight your enclosure, the better the insurance policy you have.

How to keep floor beams where they should be – inside the airtight layer

Using SOLITEX membrane to pre install airbarrier around rim joist of 2nd floor passivehouse1nz

If you can avoid it, keep beams and joists from going through your continuous “red pencil line” airtight layer. Simple means to do this is running your airtight layer over your ground floor (tape the plywood), and under your roof (taped vapor variable INTELLO membrane under the beams). However, if you have a floor within your thermal and airtight envelope, you would still need to deal with the joist that carry this floor.

Wrapping a strip of SOLITEX around the joist for an airtight layer

In new construction you can and should design the airtight layer around these issues. You can wrap SOLITEX membrane strips around the joist as shown above and to the right. Of course you need to plan this well, as the membrane has to be installed before the joist are set, and need to be wrapped around these joists (optionally around the rim-joist too) and over the floor before the 2nd story wall is build. It can be durably connected with TESCON Vana tape when the interior airbarrier (Plywood, OSB, INTELLO) is installed.

Another way to deal with this, is the method as described by Gregory La Vardera on his Lami Design blog. It simply continues the airtight layer straight on the inside of the service cavity and uses a ledger board to carry the joist – no more difficult wrapping of membranes around joists needed. just straight runs – reducing complications and chances of errors which should result in an even tighter house and will allow you to get below 0.6ach50 without to many sleepless nights.

Airtight membrane and ledger board solution to keep things simple (more images at lamidesign.com)

The added benefit to last approach is the the heatflow parallel with the grain of the wood (as is the case with joist) is about 3 times as conductive – 0.38 W/mk, R-0.37/in) compared to 0.13W/mk, R-1.1/in for across the grain – thus keeping the joist ends as far away from your insulation layer has multiple benefits. Both putting the rim joist behind (some insulation as in the 3d image) as well as in Greg’s solution thus prevents a good amount of ‘cold/thermal bridging’.

Energy Use as a Fundamental Financial Metric

In a first of its kind in the US report called Recognizing the Benefits of Energy Efficiency in Multifamily Underwriting, released January 10th, and commissioned by Deutsche Bank Americas Foundation and Living Cities, the economic case is clearly made for showing lenders that potential financial savings of energy efficiency upgrades can and should be considered in the underwriting of loans – allowing for larger loans to cover the efficiency upgrade.

Deutsche Bank & Living Cities

The report, produced by HR&A Advisors and Steven Winter Associates, with assists by Michael Blasnik & Associates and the Northern Manhattan Improvement Corporation,  analyzed pre- and post- energy use of 231 retrofit projects, totaling over 21,000 units of affordable housing, that had completed the NYSERDA Assisted Multifamily Program.

The average gains measured for building owners were modest,  with heating fuel reduction of 19% and electric reduction of 7%, yet financially significant and compelling.

Other key findings include:

• Fuel measures save [much, much] more than electric measures.
• The worse the performance of the building, the bigger the potential savings upside.
• Handicapping performance goals based on overall market data enhances the likelihood of any individual building hitting projected performance.
• Risk factors are understood and there are effective and clear measures to mitigate them.

I encourage you to chew through this wonderful report here (pdf).

BUT I think this report is more important than showing a clear methodology toward financing energy efficiency retrofits and it is this:

The report infers that a building’s energy consumption is a fundamental financial liabilty in the ownership of the building.   Like property taxes and operations staffing, energy consumption is a big number on the balance sheet.  Yet unlike property taxes and operations, the financial liability of energy consumption is within the power of the building owner to  significantly reduce.  (If they can just get the financing.)

I can’t help but imagine what the possibilities could be if deep-energy and Passive House level retrofits were made part of the equation.   With 90% reduction in heating demand, the building owner and financial lender would be crazy, IMHO, not to consider the huge financial upside of a Passive House retrofit.   One step at a time, I guess….