Technical spec sheet for International Passive House Days – Nov 7, 2014

Nearly finished... Installing the Lunos E2

Installing the Lunos E2

This house is a high performance, low cost, masonry retrofit. The design approach is to “gut” as little as possible, minimize the waste produced, and to use low VOC, natural non-petrochemical products.

Air tightness
Pro clima Solitex Mento 1000, DA, and Intello membranes & Tescon tapes

Exterior walls (front & back)
Redstone PURA, a mineral-based capillary-open board, 4”, R16.25

Cellar ceiling
Roxul Comfortbatt mineral wool, 7.25”, R30

Roxul Comfortbatt mineral wool, 9.5”-25.5”, R30-90

Rieder windows and doors
Douglas Fir Frame, Oiled Finish – 3 layer wood construction
triple glazing, R 10, SHGC-Value 51%, 30db

Lamilux FE skylight & exit hatch
triple glazing, R 9.5, 30% SHGC, visual transmittance 0.60
upstand of 7.9″ (200mm) insulated with 2-3/8″ (60mm) PU foam (0.023 W/mK)

Garden apartment
Mitsubishi DMXZ2B20NA 20,000 BTU heat pump (outdoor)
MSZGE06NA & MFZ-KA09 mini splits (indoor)

Upper duplex
Mitsubishi DMXZ2B20NA 20,000 BTU heat pump (outdoor).
Mitsubishi MSZGE12000 minisplit & SEZKD09 ducted (indoor)

Lunos e2 “through wall” (3 pairs, one per floor)
Ventilation rates: 10/15/20 CFM or 9/18/22CFM
Heat recovery efficiency of 90.6%, humidity recovery: 20-30%
Lunos e-go “through wall” (3rd floor bathroom)
Ventilation rates: 3-12 CFM in heat recovery mode, up to 27 CFM in exhaust mode
Heat recovery efficiency of 85%, humidity recovery: 20%

Hot water
2 GE GeoSpring Hybrid heat pump hot water heaters GEH50DEEDSR (1 per apartment)
50 gallons, estimated yearly electricity use: 1830 kWh per year, energy factor (hybrid mode):2.4

Keeping warm

The three pigs and their building materials

The three pigs and their building materials

When I was a child I read about the three pigs that built their homes – each from a different material. The hero was the pig who favored bricks as his home could withstand the wolf’s best attempts at demolition. While the moral may hold from a structural point of view, the opposite is true when it comes to thermal resistance. In fact, it is the straw-house pig that is sitting pretty from this point of view.

“R-value” is how thermal resistance is measured. It is the ratio of the temperature difference across a material under uniform conditions. It’s shorthand for understanding insulation worthiness of any given material. R-value per inch, allows one to compare apples to apples. In many circumstances, such as when internally insulating a townhouse in New York City, space is precious. A weaker insulator means building a thicker wall and that could mean less living space. As you can see from the chart below, common materials differ markedly in their ability to insulate.

r value chart

Thermal resistance of common materials

We took a hole saw to our front and back walls to take a look inside.  As I mentioned in an earlier post, these walls – the external walls – are crucial to the insulation.

Cross section of our front exterior wall made with a hole saw

Cross section of our front exterior wall made with a hole saw

Our existing front wall is a sandwich of (from exterior to interior):

4” brownstone + 11” brick + 2 1/8” air + 3/8” wood lath + 1” plaster

When we add the R values of these materials together we get a total of about 5.5 R.  The rear wall is similar with a little less air and, of course, no brownstone cladding. 5.5 R is not a great insulation value by contemporary standards. But as we shall see in future posts, raising the thermal resistance in an old masonry house is not such an easy task.

A couple of weeks ago we brought together three experts to help us brainstorm on approaches towards a budget retrofit: Thomas Brouillette, a (green) general contractor, Julie Torres Moskovitz of Fabrica718, a passive house architect, and David White of Right Environments, an energy efficiency consultant. It was a productive meeting though we did not come to a final conclusion regarding our approach. David White modeled two possible insulation scenarios: the near passive house approach and the minimalist approach.


Brainstorming about low budget green solutions in the backyard

In the first example, we insulate the house to R13 in the cellar, R6 windows, R16 walls, and R31 roof.  With this scenario, we would be able to use a ductless heat pump to heat the house. The end result is to get the total yearly energy consumption to about 8000 kWh per year and that is more or less what solar panels on our roof could provide. So that seems like a good target.


Near “passive house” approach

The second, and somewhat cheaper approach would be the same except to keep the walls as they are at R5.5 insulation. That brings our energy consumption to about 10,600 kWh. Much more than what it would need to get to “net zero” but not bad compared to the current energy inefficiency of the house. The main drawback of this approach is that it would not be possible to heat a house like this with a ductless heat pump – which is cheap to install and very efficient. Instead we would have to keep the existing steam system (very inefficient) or upgrade to hot water radiant heating (efficient but not cheap to install).

Minimalist approach

Minimalist approach

Both models count on tightening the leakiness of the house to 2 air exchanges per hour at 50 Pascal pressure or 2 ACH50 (that’s far short of the Passive House standard for retrofits – 1 ACH50 but nevertheless a hard bar to reach) . In a previous blog I talked about the airtightness envelop. The air tightness, in practice, is measured by a blower door test and the result of this test is your air exchange value (the number of air exchanges per hour that happen at a given pressure). At this same meeting, David White did a blower door test on our house and results were astoundingly bad (around 20 ACH50). So we have a long way to go in this respect and I will be writing more about this in the future posts.