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Posted from: MD, USA

Roof overhang framing is now going up. You can see it beginning on the south (front ) facade in the photos below. Dormer overhangs will be applied in the same way.

And NBC-TV 4’s Wendy Reiger recently profiled the project.

The Short Answer
We define true cost of ownership as the total payment per month for energy, mortgage principal, interest, and taxes.  It turns out that this house will be considerably less expensive to own than an average comparable house of the same size. The bottom line monthly cost of ownership for this house was lower—all due to the lower energy costs. As energy costs rise, the difference becomes more significant.

This is spelled out in greater detail below. While we did our best to use conservative numbers and historic cost data, we cannot guarantee these numbers.  For those who would like to review the spreadsheets that produced these numbers, please contact me at david@greenhaus.org and I will be happy to share them and to receive input. All comments appreciated in the comment box below as well.

Comparison with an average house of the same size…
The table below compares purchase of our Passive House against purchase of an existing Bethesda house of the same size and features, but with only average energy performance. In both cases we assumed a purchase cost of $1,688,000. In both cases we assumed a 20% down payment with a 30 year fixed rate mortgage at 4.85% interest.  Payment includes principal + interest + tax + insurance.

 We looked at the monthly cost of ownership (note payment plus energy cost) for each house in three separate scenarios assuming differing increases of the annual cost of energy, starting at 1% and ending at 5%.  As a point of reference, annual energy cost increases over the past 30 years have averaged around 5%. Our results are shown in the table below:

Conclusion:

The Passive House is less expensive to own from the very first month, even with its incrementally higher first cost. As energy costs rise, those savings become significantly larger.

Posted from: MD, USA

Thanks to Al Cobb for the last post!

And thanks to Terry Hill, who took the picture above this morning. As you can see, the main roof and dormer roofs are now up. The next steps will be for PanelWrights to add the framing for roof overhangs and porches, and add the additional layer of insulation that will clad the SIP walls. They will then install the windows and we will be ready for our first blower door test.

The picture below shows the top of the SIP walls at a corner, ready to receive the roof panel. The white plastic you see on top is the continuous sill sealer being installed.

The next photo below shows the sill sealer pulled back to reveal the continuous bead of sealant run under it. This is an extra step PanelWrights is taking to guarantee no air leakage here. Sealant can be seen just where the sill sealer meets the wood.

This photo shows the SIP now in place over the corner. Sill sealer has not yet been applied to the adjacent wall. The membrane you see hanging down below the hip beam is the double stick tape used to seal all joints between SIP panels. It is laid down over the hip beam before the SIPs go in. When both SIPs are in place, the paper backing is removed and the membrane adhered continuously to each panel. The next photo shows the same corner from the exterior. The recess of the foam back from the edges of the panel is for the 2×12 edge band which is not in place yet.

Here is the same corner from below. You can see the sealing membrane hanging down by the beam, not yet adhered to the panel.

And here is the peak, just set in place.

Wednesday I leave for the Passive House Conference in Portland, Oregon. Very much ooking forward to comparing notes with those doing projects in other parts of the country.

Walls Are Up

Posted from: MD, USA

We now have all SIP exterior walls and framing in place up to the attic floor. Al Cobb, President of Panelwrights, will soon be adding some posts and pictures about the erection of the SIPS and how this Passive House project is different from a standard SIP project. Stay tuned.

Posted from: MD, USA

Nearly a solid week of rain, luckily after backfilling was essentially complete, has slowed us down for the moment. These are pictures I took last week at the site before the rains began. You can see the first lot of SIPs laid out ready to go up. The film strips show the workmen carefully applying the sealant to one of the bottom plates before installation,

and then setting the plate in place.

The last picture shows the plate in place and with one-part foam insulation at all gaps.

A SIP panel with a 1-1/2” recess in the bottom will now go down on the plate, with its OSB sides anchored to the side of the plate. A bed of one-part foam insulation will be sprayed onto the top of the plate just prior to setting the panel.

Here is a link to the video on a Passive House in Vermont in today’s New York Times. 

To read the entire article click here.

We take issue with one statement: “It has been a good deal more expensive to build, however, than the average home.”  Using readily available technology and products, this has not been true in our case. We had each subcontractor price out the differential cost for the Passive House components in his work— foundation work, heavier SIP panels, extra insulation, upgraded windows, mechanical systems, etc.  We then compared the development costs of this house versus the cost had the same team built it as a standard good quality, well-insulated house. We found that the increased cost for this house is about 8%.

The real issue to look at with regard to cost is the true cost of ownership: monthly mortgage payment plus monthly utilities cost. I will be posting something soon comparing our house to a conventional house of the same size in those terms.

No, we didn’t finish it quite this quickly!  But we finally have a rendering.. thanks to the efforts of Nick Hester, SketchUp artist extraordinaire! Nick graduated a year ago from Mississippi State’s architectural program and worked for the past year with Pliny Fisk at the Center for Maximum Potential Building Systems in Austin. We are lucky to have him helping us out.

Posted from: MD, USA

Floor framing and decking are now complete. Here are a few pix of the work in progress. The ladder you see is in front of the first SIP panel installed— the north basement wall.

Posted from: MD, USA

Today PanelWrights arrived onsite and began preparation for the basement wall and first floor framing work.

 When I arrived they had already set down the 2×8 treated wood plates at the top of the foundation walls. These sit on top of a sill sealer and and added layer of sealant, and are fastened with steel bolts down into the concrete. You can see the plate at the top of the walls in the first picture.

 While some men were setting the wall plate, others were caulking the joint between the concrete slab and the foundation walls. I wrote in our Aug. 8 blog post that we were going to use a termination bar to seal the StegoWrap vapor barrier to the foundation wall. Keith came up with a better idea: cut the StegoWrap at the top of the slab and embed it in sealant. Katrin Klingenberg liked the idea and suggested we add a layer of butyl tape over the sealant as an insurance measure. In the second picture you can see the sealant to the right and the butyl tape to the left as it is being applied.

 Katrin also recommended that we apply 2” of EPS rigid foam to the interior face of the foundation wall. The idea behind this is that with the extra insulation we are ensuring that there will be no condensation of any warm moist air on a cold concrete surface. In the third picture you can see the rigid EPS board set against one of the foundation walls. The yellow stuff you see is closed cell foam insulation from a can (GreatStuff). Just prior to installing each board of rigid insulation, they sprayed a bead of this stuff at the bottom and the sides of each piece, then pushed the rigid boards into place. This is simply an added measure of security to keep the wall airtight and eliminate any gaps in the insulation. Like most things in Passive House construction, rather than using expensive and hi-tech new products, we are simply taking a little more care in how we put the house together.

 As I left the site, the PanelWrights crew was putting down the treated pine floor plates for the stud walls that will go up inside the foundation walls. You can see the this in the fourth picture. Tomorrow the steel posts and the central bearing steel beam will be set in place and the floor framing will begin. That should be complete by Thursday. 

 The last picture shows one of the SIP wall panels which are now being delivered to the site. You can see that the foam is recessed at the edges. This is done so the panel can straddle the top of the wall plate and the OSB sides anchored to the plate. More on this as they begin going up in the next weeks.