We used Structural Insulated Panels in the building of this Net Zero Energy home.

Structural Insulated Panels (SIP) comprise the bulk of our outside walls They even separate the house from the garage/shop.  We chose this type wall primarily because they exhibit an outstanding insulating R value of 30.  This section of text will describe several techniques we used to increase the overall energy efficiency of our home.

First let me show you a very rough outline of the perimeters of our home and shop which are connected under a common roof.  Please take notice that the outside walls have a minimum of an R30 insulating value.  However, there are portions of the perimeter that actually sport an R40 or R50 insulating value.

Rough House Drawing

                         Structural Insulated Panels surround the entire perimeter and comprise the wall between the house and shop.

The crew started assembling the Structural Insulated Panels by placing them on the aged concrete.

Concrete enveloped studs formed the mounts for the Structural Insulated Panels.  The bolts also held the the walls tightly against the pressure treated sill plates. A large construction fork lift help place the panels in the proper position before completing the fastening operation.  Note the concrete pad that I did not have picture of to present in prior text section.  You can also see two shop window openings are already outlined in place with the header and encased 2X4 mounting studs.  This photo shows the Structural Insulated Walls as they were being assembled over the pressure treated sill plates.


Structural Insulated Panels installation jin process.

Structural Insulated Panels being installed over bottom plate attached to concrete pad.


The outside perimeter building walls consists of:

  • Six inch R 30  Structural Insulated Panels (SIPS)
  • Marvin dual pane R 3+ windows
  • ThermaTrue outside pedestrian doors R 7 (?)
  • 14 X 14 foot overhead garage door (R17.5)
  • 12 X 8 foot overhead garage door (R 17.5)
  • Extra outer layers of EIFS insulating exterior covering

Additional insulation was applied over The Structural Insulated Panels to overcome thermal bridging.

Window and door frames typically yield only an R2 insulation value to a surrounding wall.  We overcame that potential for excessive heat loss in a couple ways.  First we used a foam/stucco EIFS (Exterior Insulation and Finishing System) over the entire house outside walls.    The EIFS siding gave us an additional four inches of R16 foam over all window and door thermal bridging areas.  It also yielded an additional three inches of R12 foam and stucco over all other areas.

I installed another one inch fiberglass covered R8 foam board under the inside of the drywall.  I cut it snug with the door and window jambs to cover all thermal bridges made up of multiple studs in most cases.  So, all this added to make a total of about R 26 over thermal bridging areas with virtually no chance for fenestration.  The non-thermal-bridging areas boast an average calculated total insulation value of R50.  We did have to install window jamb extensions after we had already received the windows.  Also I had to mount the electrical boxes out further than normal.



Extra R8 Foam board under drywall reduces thermal bridging.

This foam board with fiberglass surfaces reduced thermal bridging from the inside and added to over wall R values.

The wood studs produce only an R2 of insulation value without the additional insulation being placed over the those thermal bridges.   You can compare that to R30 from the Structural Insulated Panels alone.  When you increase the insulating factor from R2 to R26, you reduce the heat loss through that area by 15 times.  Before and after pictures of the EIFS treatment over thermal bridging areas appear directly below.



All the thermal bridges stand out between the windows and the Structural Insulated Panels in this picture.

Outside Thermal Bridge Extra EIFS Insulation

This picture shows the walls around the windows and door when EIFS has been applied to the Structural Insulated Panels.  We think the detailed trim also presents a pleasing appearance.


We utilized and will utilize more EIFS material for other applications as well.

The EIFS applicators also placed an additional layer of the stucco over the top exterior of the insulated frost wall.  This application extended to well below grade level all the way around the house and shop perimeter.  That extra work made sure that we had a very good seal against air penetration getting through the joint between the frost wall and the SIP walls that rested on the SIP base plate.  It may also help keeping insects out of the house as well. This extra insulation added a bit more resistance to thermal bridging through the base plate as well.

We did not finish the west bedroom outside wall with the EIFS siding but used concrete siding instead.  Hence, that wall offers only an R value of 30 thanks to the  Structural Insulated Panels plus less help from as much foam.  The interior R8 for the foam board under drywall and R2 for the associated wood and drywall still total a whopping R40!

The winter weather kept the bedroom colder than the rest of the house so we thought we had made a mistake not finishing the west siding.  Instead, we discovered that the problem was some missing spray foam between a cross wall and the outside wall.  The problem actually caused a separation issue in the bedroom corner so we hired a carpenter to repair that bad situation.  We have not experienced any fenestration issues from high westerly winds since the repair.   Thankfully the bedroom stays nice and warm even when the outside temperatures drop significantly.  I doubt we will have to finish the outside wall with EIFS any more.


EIFS stucco/ foam coating over the frost wall at the RV hookup station.


High quality wood casement windows and shades complement the Structural Insulated Panel walls.

The windows were selected because of their fair R value over the window portion and their outstanding fenestration (air infiltration) ratings.  We have purchased R4 value triple-combed window shades to help reduce excess winter and summer surplus passive solar heat gain.  The shades will also reduce winter night time heat loss through the windows significantly.  We have waited to install the shades until carpeting and tile work is done so as not to fill them with dust.  Most of the other dust making work has been completed, so we will proceed with the shades soon.


The Marvin Casement Windows are about nine inches thick owing to the Structural Insulated Panels and extra insulation inside and outside.

The view to the south which is also great for maximum solar production thanks to there being no obstructions.  Future landscaping will have only low growing vegetation, gravel islands and a pond.


Structural Insulated Panels form a nice heat and sound barrier between the house and shop.

The north wall of the house runs the length of the building between the house and the shop.  It also is formed by the using six inch Structural Insulated Panels for an R value of 30.  The highly insulated wall reduces heat losses from the house to the shop during the winter when the shop temperature might be maintained at only 40 to 50 F.  Any heat lost through this wall is not wasted.  The heat pump will simply work less providing heat to the shop floors.

Outside temperatures in the first winter fell below minus 30F for a few days and minus 20F for night time lows over a period of perhaps a few weeks at a time.  During that time, we were able to maintain the inside house temperatures at about 72F while the shop was held to 62F.  This was all done with a single three ton ClimateMaster heat pump, thus keeping 5200 square feet very comfortable during the coldest winter months we have had in years.

Structural Insulated Panels provided a defense against the outside cold.  Stick framed interior walls were also insulated, but for sound attenuation.

The picture below clearly shows the use of both Structural Insulated Panels and stick built framing.  The architect designed two vertical walls above the normal nine foot high ceiling.  Those walls provide additional height in the ceiling to provide a motor coach bay.  Those and the west end of that vaulted ceiling are the only non-SIP walls exposed to the outside temperatures.  Therefore the insulators filled those two walls with high density spray foam.

It is interesting to note that we built our home throughout the seasons.  Even the cold winter weather was not terribly uncomfortable if you simply dress properly for the conditions!




The Structural Insulated Panels are supporting the recently installed trusses in this picture.  The SIPs also form a wall that is not visible between the house to the left and the shop on the right.

We took the picture below while the roof trusses were being lowered into position by a crane. Structural Insulated Panels and some stick framed interior walls support all the trusses.  You will see the six inch foam inside the SIP wall if you look at the extreme bottom of the following picture.


Someone took this photo from the covered patio looking through the 70 foot house length.


R8 fiberglass coated foam boards cover the shop windows in the winter.

We left the shop unfinished and it will probably remain that way as long as we own it.  A total of six outside Marvin R3 dual pane windows keep the shop space well lit during the day.   In the winter months I place some 4 X 8 foot one inch R8 foam boards over each of the windows to cut heat loss by an additional 87% compared to the bare windows.

I typically leave translucent coverings over the shop windows during the spring, summer and fall months.  Those coverings allow more light in to reduce the need for active solar power production. The contractors mounted all the windows within the six inch SIP walls that have 5/8 inch plywood sheathing on both sides of the foam interior.  This plywood provides a perfect way to simply use some 1.5 or 2 inch long wood screws to mount the foam boards and translucent covers.  I don’t worry much about esthetics because the walls are unfinished.  Unfinished walls make the application and dismantling jobs each fall and spring respectively very quick and easy.

I obtained my boards from Home Depot.  They came with a thin fiber glass sheath that helps protect the boards.  However you should wear gloves to protect your hands from splinters.  I would like to caution anyone thinking of using this foam insulation idea.  Do not leave any foam window covers on when the western sun shine through brightly.  When I did so, I wound up with broken glass and a shrunken window jamb.


4 X 8 foot sheets of foam board placed over shop window and fastened into the Structural Insulated Panel.


Insulated overhead doors complement the low heat loss features of our Structural Insulated Panels.

The Overhead Door Company manufactured our two overhead doors with a claimed R 17.5 insulation rating.  A 14 X 14 foot door offering such an R rating was better than I expected. We also applied EIFS siding over the top and sides of the large door jambs to cover all the thermal bridging areas.  Like all the other doors and windows in the house, this provided an extra bit of protection against heat loss.

A special door sealing strip of of paint brush like bristles nicely stops all air intrusion around the doors.  A strip of extruded aluminum contains and restrains the long brush strips.  The door installers fastened the aluminum strips by using long screws.  The screws had to penetrate through the foam and into the door jamb.

The door slides past the brush seal until the door is fully closed.  Once closed, the brush bristles seal  well against the door. I can feel no drafts through the brush seal even when outside temperatures are minus 20 or 30F. I can highly recommend this sealing system for the sides and tops of the overhead doors.  The plastic gaskets never sealed well and they seemed to wear out fast for me.  The brush seals do cost more, you can be sure.

The bottoms of the doors form a good seal with a compressible plastic door gasket.  You must keep those gaskets maintained to avoid air penetration as well as mouse penetrations.


The large shop door shows off the brush seals on the top and bottom and the rubber bottom gasket.

This insulated steel door upholds the good insulation theme of the Structural Insulated Panels.

In Conclusion.

This section turned out to be longer than I ever expected, but I opted for more pictures.  It seemed that more photos would contribute their 1000 fold increase in information as opposed to trying to describe everything with words.  I hope you agree and I welcome your comments.

Thanks again, Mike.