Installed first skylight

I have not posted about earthship construction since we installed the flashing along the south edge of the roof … we have been doing some work since then.

Our goal this spring (it has now officially been summer for a couple of weeks) was to finish some of the roofing details that we did not get around to last summer; this included flashing along the south edge of the roof (and along the sides of the kicked up portion of the roof), installing skylights and finishing the roof over the south door.

We flashed the south edge of the roof back in June, and we also flashed along one side of the kicked up portion of the roof a few weeks ago.  Flashing along the edge of the kicked up roof was virtually identical to flashing the south edge of the roof except that we also had to account for the change of pitch in the roof at the junction of the greenhouse roof and the main roof.  We solved this issue by cutting and bending the flashing.  Our solution along the side works but we expect it will change; we want to put a small roof over each side door to protect them from the weather so we will have to accommodate these roofs at a later date.

With the roof flashing well in hand we also turned our attention to the skylights last month.  We built our skylight boxes (or wells as they seem to be referred to commercially) as specified in Earthship Volume I.  We built 4’x4′ boxes out of 2″ dimensional lumber that we centred on the rafters where we wanted them in each room.  This worked well and we simply finished around these boxes as we were insulating and installing the roof membrane.

We initially planned to build our own skylights as is described in the Earthship volumes, but eventually decided in favour of commercial units.  We did not pay attention when picking our skylight locations in each room … the Earthship Volumes suggest placing the skylights as far back north in each room as is possible.  The north location ensures better ventilation and means that you are close to a wall.  The skylights described in the Earthship volumes use cantilevered weights and a cleated rope that dangles down from the skylight for opening and closing.  By placing the skylight as far north as possible you ensure that the dangling rope is close to a wall where a cleat can be installed and the rope can be tied off out of the way. Due to our skylight placements in some rooms the rope would be dangling down without a convenient wall to cleat to … not a good finishing detail.  Much more importantly I was not comfortable that I could build a unit that lasted a long time, was worried about leaks and at the end of the day was not convinced I would save much money by building my own operable skylight once I had purchased all of the components.

I found out fairly quickly while shopping for skylights that the industry standard for a 4’x4′ skylight well is to build it 4′ on centre (which makes a lot of sense as framing lumber is typically 16″ or 24″ on centre) … as opposed to the 4′ (outside edge to outside edge) that I had built.  This meant that we had to modify the tops of our skylight boxes by attaching a 2 – 1/2″ x 2 – 1/4″ wooden adapter plate to the tops of our wells so that the skylights we purchased would fit.  Building this adapter turned out to be more tedious than complicated; the flashing at the top of the skylight well had to be cut away, the adapter ring installed and then the top of the well and the adapter had to be re-flashed.

We purchased our skylights from Dayliter Skylights in Langley, BC.  We saved on freight as we (or relatives) frequently pass by Langley.  These units have a double layer of safety glass and an acrylic dome on top.  Once we fixed our wells installation was very simple, and I am pretty confident I could not have built a unit of comparable quality.  Each unit was approximately $600.00.

We installed our first skylight on Saturday (thanks James) and finished our second one today.  It is amazing how much more light there is in these rooms!  I noticed this evening when we went out to finish the second skylight that it was brighter in the back of the earthship than it was in our current dwelling at the same time in the evening … passive lighting really does work!

James took a lot of pictures of the first skylight we installed and I hope he posts them soon!  Hopefully we will install the remaining three skylights this coming week …

 

Tempered Glass Glazing … Who Knew?

Many things we have done on this project were simply unknown to us before we started;  we are learning all about traditional plasters, we’ve built our first flat roof … and I now know way more about tire sizes than I ever hoped to!

Surprisingly (to me) specifying and ordering the glass has turned into another learning experience.  Surprising because we have specified and ordered plenty of windows for past projects.  But, just before ordering we found ourselves scratching our heads over tempered glass, one-in-ten wind speeds for the Kamloops region and building code requirements for windows in a residential building.

Normally (at least in all of our past building projects) I draw up a set of plans showing window location and sizes.   The plans are passed on to the window and door manufacturer working on the project, who then assembles a package of windows compliant with the Building Code.  This process is relatively simple and has always been fairly straight forward.  Of course in this project we are building most of the windows ourselves and the majority of the glass is going into a sloped green house wall, things we have never done before …

The British Columbia Building Code (2006) has a fair bit to say about the windows in a residential building. There is a basic requirement for a minimum square footage of glazing in rooms that is specified as a percentage of the floor space of the room.  Living rooms and dining rooms require ten percent glazing and bedrooms must have at least 5% glazing.  So a 100 square foot bedroom would require at least 5 sqft of glazing.  These specifications are considered the bare minimum for passive solar lighting of a room during daylight hours.

The Building Code also has safety requirements for glazing relating to proximity to doors, the ground or the floor and the shower.  These safety requirements exist to prevent you from accidentally breaking the glass from falling through it  or shattering it by slamming a door, and if you do break a window from hurting yourself on the shattered glass.

The residential Building Code does not have much to say about glass in a green house.  However, it does specify that overhead glazing (like a skylight) must be made of safety glass so that large shards of glass cannot rain down on your head if the window breaks. Tempered glass meets this requirement since if it breaks it crumbles into little pieces (think car glass).

The specification in Earthship Volume I for the fixed greenhouse glazing units calls for ‘… double-paned, insulated glass …’ and ‘… stock glass units, 1″ thick …’.  Further, you need to ensure that the glass is not low E or tinted.  Many of the processes that improve the insulation of the glass retard the solar gain needed to make plants grow and to heat your building.  However, I do not remember any discussion of using tempered or safety glass for the sloped green house glazing. Can anybody clarify this based on their reading?

I searched the internet and did not find any definite specifications calling for tempered glass for the south wall earthship glazing.  However, most of what I read on the subject of sloped glass, overhead glass and green house glass consistently recommended using tempered glass for these applications.  From a website about construction and renovation issues,

…  my opinion as a professional inspector … if there’s any chance that based-on the position of these windows that someone inside the home (usually small or young children) or outside the home (gardener, you yourself, a careless drunk walking-by, etc.) could accidentally (or otherwise) impact the glazing, put in safety glass. It’s the best modern construction practice, period …the disclaimer: All information provided above is based-on contemporary NATIONAL building codes and practices. Your mileage may vary …

and I did find a few references to using tempered glass specifically in an eartship,

What about hail? Won’t the slanted glass break? … Wherever large sheets of glass are exposed to wind, ‘small’ projectiles and the elements, they should be tempered glass and in most places, it’s required.  Tempered glass is very difficult to break and when it does, it doesn’t break into shards of cutting pieces, but rather thousands of small, almost ‘granular’ pieces.  The slanted glass indicated by many passive-solar designs must be tempered glass.  Our window array has withstood 2-1/2” diameter hail, so far [crosses fingers, knocks on wood].

We have chosen to use tempered glass units for all of our green house glazing.  This glass is about 25% more expensive than standard units, but will hopefully minimize any issues down the road.

Since we are building the fixed windows ourselves, I also did some research on the ability of these units to successfully resist wind loadi ng in our area (in other words not shatter due to a wind storm).  It turns out that hourly wind speeds that have one chance in ten of being exceeded in a given year are used to specify glazing units.  In the Kamloops region our one-in-ten hourly wind pressure is 0.3 kPa according to Appendix C of the 1998 building code (I am using the 1998 values as these tables are no longer specified in the 2006 version of the code in favor of a separate document).   According to Table A-9.7.3.2.(1)A of the current BC Building Code (2006) 5 mm tempered glass works for our largest window size.

So, all of this results in the following specification for our fixed windows …

The fixed windows will be sealed, double-paned, insulated glass glazing units (1” thick) (tempered, regular 5mm glass).

Seems like a lot of work for that one line doesn’t it?

Our operable units will be standard tan vinyl sliders with a 3.5″ jamb to match our window framing.

We have not specifed our skylights yet, but it looks like we will use triple-paned units (made of safety glass) with a low E coating on one of the panes.  We do not want heat gain through these units.

The Roof Is Bermed!

Alvin came back today and bermed for the final time around the back of the building!  This event feels like a real milestone as we will FINALLY move off of the roof and start working on the front wall in earnest …

This berm comes up over the back of the roof and actually covers a foot or more of the roof perimeter.  We laid a five foot strip of geotextile fabric around the perimeter of the roof (half draped over the edge of the roof and half running down the berm).  I wanted to provide some additional protection for the EPDM roof membrane where we are covering it with soil.  The picture to the left shows one of the drainage channels (we have three total) at the back of the roof.  For now the drainage channels simply run down the berm.  Eventually we will route the drainage channels to cisterns and collect our roof rain water for irrigation.  We laid stones down along the edge of the final berm so that Alvin would have a guide for placing dirt.

This is what the roof now looks like.  The skylight openings are covered with 4×4 sheets of particle board and lumber wrap.  We will probably build/install the skylights as we are working on the front wall.