Blog

Chris Conway and crew were able to get back at the site on September 3rd for a second test, after taping of the various leaks we’d uncovered  on August 26th. The big culprits, we believe, were the gaps at each of the straps between the top and bottom modules.

The results: .40 ACH50Pa.  Our tightest house yet!

Here are a couple of before and after taping shots:

straps before

straps after

damaged floor tape

re-taped floor

 

Chris Conway and Caleb Fritsch of Conway Energy performed the long-awaited blower door test for our first modular passive house today. We couldn’t have picked a more beautiful — and simultaneously more inopportune — day to have scheduled it. Good forensic testing requires a greater than ten degree difference between inside and outside temperatures so that a thermal imaging camera can “see” the temperature differences where air is leaking. For example, when the interior of the house is cooler than the outside air, leaks coming in will read as orange or red plumes against a blue background during a depressurization test. Conversely, in a pressurization test leaks from within will show up against the outside of the house as blue plumes against an orange background.

Trouble was, on this August day the high was a balmy 78 degrees and we had only been able to get the interior temperature down to 72 degrees with the single window unit we had hooked up to the generator! (The main cooling system could not be run since the house is not yet connected to the grid.)

So the ever-resourceful Chris pulled out his smoke pencils, which were better than nothing. With them you can spot leaks by the change in direction of the smoke as you pass it over a leak. But it is far far more tedious and less efficient that using thermal imaging. We were able to use the camera in the attic space, however, which was well over 90.

It was a nervous moment when Caleb started the fan. The result: .65 ACH50Pa (air changes per hour at 50 pascal of pressure) on our first try. We were delighted with that number, having had no idea what to expect. Chris found enough leaks with his smoke pencil that, in his view, we should easily get below the required .60 ACH50Pa by fixing them.

Most of the leaks were beginners’ mistakes, which we will chalk up to lessons-learned. All are easy to fix:

• The taping of the joints at the first floor subfloor had been damaged by foot traffic in a number of places in the course of the construction. We will re-tape those joints , and in the future we will make sure the subfloor tape is covered by a protective layer during construction.
• The men taping the joint between the top and bottom module had run the tape over the metal straps that connect the two modules, thereby leaving a crack every two feet or so where the tape was discontinuous. This led to a number of leaks around perimeter at that line. It is an easy fix, and avoidable in the future by taping before the straps are bent into place.
• While factory penetrations were all sealed by rubber gaskets and tape, the penetrations made in the subfloor after the house was set were only sealed with foam. Vince will cut the foam back and seal around each of this penetrations with a sealant gun, and tape where appropriate.
• We forgot to tape the overflow holes at bathroom vanity sinks. Right now these are holes to the exterior since the plumbing is not yet hooked up to the sanitary sewer line to the street.
• The attic hatch doorway, provided by Conservation Technologies, was remarkably airtight. It leaked, however, around the rough opening in the framing where in which it was installed. They had used foam to seal that gap rather than air seal tape. Again we will remove enough of the foam to allow a continuous band of tape around the frame.

John Meredith and his crew at Beracah Homes should feel very proud to have achieved this test result on the first try of their very first Passive House.  It represents a very meticulous assembly process. To put it in perspective, the leakage recorded today is the equivalent of roughly a 3″ diameter hole in the entire building envelope. Chris reckons that by reducing that figurative hole by 1/4″ we will achieve the .60ACH Passive House standard.

Here are a few pictures from the day…

   finding leaks with the smoke pencil in torn first floor taping

the interruption in the taping between the top and bottom modules — no need for a thermal imaging camera to see these gaps!

the view from the inside of the gaps shown above — note the steady directional stream of smoke.

foamed site-made penetrations at the first floor — the foam will be cut away flush with the floor surface and sealant will be applied around each opening. Same drill will be performed at the bottom surface penetration.

This infrared photo shows the attic floor. Angled lines in the background are the rafters. Those in the foreground are the framing for the midspan rafter support. When we saw that big patch of blue we figured there was a lot of air somehow escaping from the house into the attic. A closer look revealed that the area was still damp from where the solar panel folks must have spilled some water during installation of the panels. The blue is caused by evaporative cooling!

Looking down at the attic floor and the folded up attic stair. The blue shows leaks between the attic framing and the frame of the attic stair unit. This was foamed not taped, and this shows why we prefer tapes.

Architects rarely see sudden transformations. Our work is composed of small incremental steps, generally forward, from fuzzy concept to finished building. The pace usually seems glacial and there is never, ever, a big WOW moment when what we do suddenly becomes a building. So it was a unique experience today watching our first modular house go up. To see a site go from empty foundation in the morning to fully erected and enclosed house in the afternoon — that was indeed a first for us!

Things began quickly. They had brought the modules over from Delaware on Monday and parked them in a nearby parking lot, so they were at the site by 8. The first floor was a bare box. The second floor box had the folded up roof on top of it. By 9:30 the first floor module was already on its foundation.

The second floor module took more time, as the set crew decided to completely erect the roof while the unit was still on the ground and more easily accessible. Also safer to fall from 9’ rather than 19’ if there were an accident. So the rest of the morning and early afternoon went into the process of unfolding the sections, attaching the eaves, then tilting the roof up into position. It was a beehive of activity with a crew of about 15 men and boys all busy all the time. Around three, things got very quiet, the hammering stopped, and all the workmen stepped back to watch the crane operator do his magic. Lifting the second floor and roof into place took exactly six minutes. Voila, we had a house!
Here are some of the high points in photos….

Last chance to clean up the crawl space

8 am. Waiting for a house.

9:30 am. First floor on the foundation.

 

                                              Perfect fit!

The hold-down metal straps are embedded in the concrete and will now be fastened to the structure.  The factory-applied blue Tescon Vanna tape makes the seam between the sheathing and the rim joist airtight. Another piece of the Zipwall sheathing (the green stuff) will now be anchored to the wood sill plate below and the rim joist above to make the whole assembly monolithic.

These metal straps will anchor the first floor module to the second floor module. The taped up box you see there is a junction box for one of the exterior awning motors.

The cheering section: Brendan O’Neill with Jocelyn Harris and Maryann Dillon of HIP

The second floor module now pulled into position. Note how the right side of the roof is of one piece but the left side is made up of two segments with an elbow. This is done so that they will lie as flat as possible for shipment down the road in order to stay under the maximum shipping height limits.

Loading the eave overhangs onto the deck from the truck. They have to be added at the site; otherwise the width of the unit would exceed the maximum shipping width limits.

Beginning to attach the eaves to the rafter ends.

More of the same.

Meanwhile Vince Coffin, our jobsite supervisor, adds some more Vanna tape as an extra sealing precaution.

Eave overhangs now in place.

Inside the first floor module Brendan O’Neill and Vince Coffin confer with John Meredith. John shepherded the house through the factory design and construction process from beginning to end.

A couple of spectators in the stairway on top of the first floor module.

Roofs with their eaves attached now tilted up into place.

Inside the attic, the hinges that the rafters pivoted on.

Kneewalls,…… gables, and rafter ties all on the truck waiting to go up.

Kneewalls being delivered.

Kneewalls now in place. Rafter ties being delivered, while above men are installing the ridge vent for the roof.

Now the gable ends are set in place.

Setting the cables in place….… and running them under the module.

The metal strap is there to prevent any chafing by the cable during hoisting.

3:30 pm. Top unit in place.

Tomorrow the electrician, plumber and mechanical contractor arrive to make the hookups between first and second floor units, while carpenters finish attachments between the units and the the foundation. Then taping of the joints between modules and penetrations in preparation for the blower door test at the end of next week.

I will add video of the actual setting of the units when available.