Monday, February 10, 2014

Installing Large Size Sun Room Windows

After having built and lived in quite a few passive solar sun rooms over the last 40 years 
I have come up with a good way to set the large double glazed glass units
 that are commonly used for such rooms.

About a year and a half ago we purchased a passive solar heated adobe fixer upper
 with a very long 80' sunroom, built in the mid 1980's.

It was very apparent that the 18 fixed 1"x 46" x 76" double glazed glass units 
needed some serious work after the 30 years since they were originally installed.
Some of the stops were rotted or missing, several units were clouded over from broken seals, 
and the sill plate was vulnerable from water and insect damage.

These first two photos showing the remodeling already finished,
 give you a good idea just how big a job this was.

These glass units are a standard size and are commonly used in our area for this application.
As they do not have a finished frame around them,
I think of them as glass units or slabs, not necessarily "windows",
which I consider already having factory wood or metal frames around them.

If I was building new I would use the 1" x 34" x 76" units, which are much easier to handle and install.

As part of this project we were also installing a door in one of the window openings,
and to do this we needed to cut out part of the stem wall.

The above photo gives a good view of the problem as shown in the upper right corner. 
Rain washing down the glass compromised the original stops holding the glass in 
and was forced into a crevice between the stucco 
and the sill plate as seen in the extreme upper right hand corner.

The stucco should have never been brought up and over the stem wall and insulation,
 as this would be an impossible joint to keep sealed.
The two move at different rates from settling and temperature and moisture induced 
expansion and contraction allowing water in the void to compromise the sill plate.

If you are designing a new sun room it is much better to extend the stem wall 
a foot or so above the finished grade,
 which helps keep rain from splashing onto the glass (and sill plate).

Above gives you another view after the stucco has been removed from the top of the stem wall.

The original bottom stop for the glass is rotting away
and the redwood sill plate has also started to rot, 
making a perfect invitation for further damage from termites and other insects.

Above we have started by removing more of the stucco and insulation to just below finished grade 
and coated the exposed concrete block stem wall with 2 or 3 coats of emulsified asphalt
and sealed the joint between the wood and concrete
 with an acrylic/latex caulk formulated to be used with concrete.

Any exposed wood has been slathered with multiple coats of boiled linseed oil
 to protect from further moisture damage and protect from insects.
I should add that there is no proof I know of that linseed oil will protect against insects 
but I still hold on to that belief. 

Also above you can see one of the original vertical stops that are 1/2" x 1/2" and nailed in.
These stops are really much too small for the long haul.

The lighter colored, new Western Red Cedar stile that you see above
 is the first step in adding new facing and replacing the stops. 
I milled all the pieces on my 10" contractors table saw as you will see below,
then they were sanded and oiled with linseed oil multiple times 
then glued with "water resistant" glue and finish nailed with galvanized nails. 
The nails were set and covered with a colored wax filler.

And finally in the photo above notice the indestructible poly butyl caulk 
still attached to the bottom of the glass after 30 years.
This was used on both sides of the unit and 
even though they are a standard detail for installation it is a bad idea.

First problem in this case is the poly butyl on the inside adheres the glass to the wood frame 
which means the inside of the double glazed unit cannot float freely in the frame
 increasing the likelihood of breaking the seal between the two panes of glass letting in condensation 
and obscuring the view, necessitating replacement of the unit.

Second problem is that the poly butyl seal must be broken to remove the glass unit
and this takes a lot of work and time especially if you are paying a contractor.
Allison spent 2 full days with a sharpened putty knife tediously breaking the poly butyl seal
 between the inside solid wood frame and the 18 glass units.
 Then it had to be scrapped off the glass after we had the units removed.

I think I have a better way.

The first step was to head to the shop and cut facing and stops out of the Western Red Cedar 
that I chose for this project which took a week standing at the table saw. 
I chose the Cedar for it's resistance to decay, workability, availability and affordability.

After sanding, drilling screw holes, and oiling with multiple coats of boiled linseed oil 
I left the wood to start bending sheet metal while the oil dried. 

Above you can see the 46 1/2"+/- long pans made from galvanized sheet metal
 that will fit snugly under the glass and over the sill plate.

The long (front) edge of the 4" wide sheet metal is bent over and crimped 1/4" to 1/2"
 so there will not be a sharp edge left after installation.

The end and back edges are bent up about a 1/2" leaving enough room to staple the felt weatherstripping to the 3/4" inside stop creating a pan to direct all water to the outside 
and protect the sill plate from rot, paying special attention to the folded corners so that water will not leak out there (like wrapping a Christmas present).

Above you can see how the stops are beveled for a nice trim look, 
the felt weatherstripping has been stapled to one stop, 
and pay special attention to the grooves I made in the piece that goes on the bottom
 to allow any rainwater or condensation to move freely out over the metal pans.

I cut the grooves with a radial arm saw, the blade raised about 5/8", and the stop laying upside down.

I had stops laying everywhere, numbered and cut to length.
I never use a miter cut but prefer to cope all the joints.

I use a pre marked stop to mark all the screw holes so they are all even 
when looking along the length of the finished sun room.

The above stops are drying from the oil and waiting to have the felt stapled on before being installed.

The beauty of the felt is that is long lasting (especially when compared to foam weatherstripping),
it allows the glass to float freely within the frame, it creates a tight seal, it is non toxic, 
easy to work with, and affordable.

The only problem is that it may be hard to find anymore
 as the foam weatherstripping has taken over.
Check your local hardware stores and lumberyards
 as the big box stores don't seem to carry it.

Once we had the new facing installed we got to work on the stops.
Each glass unit was removed from the outside, and all poly butyl was cleaned off,
any bare wood was oiled, the sheet metal pans were placed 
and the back upright edges were tacked in to hold them secure. 

The felt was stapled to the inside stops, the glass was carefully put back in place,
and we screwed in the top stop first using the predrilled screw holes,
  very carefully tapping the stop to snug the glass up to the felt for a nice firm fit.

The side stops which already had been coped and cut to length were installed next,
in the same manner as you can see above.

We cut the side stops 1/4"+/- short to keep them from contacting the pan
 and potentially drawing up moisture into the end grain.
Using tin snips I cut the raised ends of the metal pans flush to the facing 
so that I can bend the extended front down to shed water.

Although very hard to see above, it is very important to set the 1" wide glass units 
on to 1/8" x 1"x 4" rubberized setting blocks which are usually are provided by the supplier.
These keep the bottom of the glass up off of the sill 
and provide a firm even base for the glass.

And finally the bottom stop is installed
 and the protruding edge of the metal pan is bent slightly down to shed water.

We later came back and put a thin bead of silicon caulk over the exposed felt 
between the stop and the glass across the bottom and about 4' up the sides
 to keep water from being absorbed by the felt.
We also put a dab over each of the bottom screw holes as you may be able to see above.

If you look very carefully above at the bottom of the bottom stop 
you can just barely see the grooves I cut across the bottom of the stop 
to allow any moisture out from the pan 
which I mentioned above as I was highlighting the shop work.

The weak point here is the screws for the bottom stop that penetrate the metal pan.
We put a bit of silicon caulk on the tip of each screw before attaching them
 in the hope that that might help keep water from accessing the hole in the pan.


                     Now in the future any glass that needs replacing will be a simple step of merely removing the screws from the stops, replacing the glass and reapplying the stops.

These glass units need replacing from breakage or the failure of the seals over time 
and for future homeowners this will make the job much easier.

We added a new door in place of one of the window units 
to access a new patio that we are currently installing in front of the sun room.

We bought a double glazed wood glass door for the opening 
but not being satisfied with the available storm doors we decided to build or own.

We used a clear 1 3/8" ponderosa from the local lumberyard,
with mortise and tendon joints.
The bottom panel is a fixed piece of plexiglas 
while the upper is a plexi panel for winter mode (showing)
 and a screen panel to be installed for summer.

And of course I used felt weatherstripping for both doors.

The square dowels are apricot.

The above photo is nearly the same angle as the 3rd photo from the top 
and shows the improvement we have made in this project.

The wood sheathing that covers the framing for the door 
is the same Western Red Cedar we used for the facing and stops.

In the photo above note the galvanized metal spacers between the sheathing 
and the concrete sill which helps keep the wood up from the concrete.

All the stops for the door panels and the door sweep at the bottom 
were cut from scraps left over from the Cedar.
Both sets of stops are screwed in with brass screws to facilitate 
changing the plexi and the screen in the top 
and repairing the bottom fixed plexi should it be broken.

The galvanized metal pan extends over the bottom door rail 
and down to the rabbet to deflect water off the rail.

I made a simple plywood template to form the concrete door sill so it slopes down from the main door.
There is a slight revel along the edge of the main door 
that you can see to help keep rain from blowing under  the door.

Thanks for reading and I hope my solution to this detail helps.