SIPs House Portland

SIPs framing

It’s been a while since our last post.  Because of the ‘jenga’ process of putting the panels together, we were on hold waiting for one little on site weld to happen.  Apparently welding in the rain is not a good idea.  We were able to slip this in between rainstorms last week and are just about finished framing.  As we’ve noted in the past, the panels, while simple in theory, are not easily assembled.  I think in the future it might be a good idea to specify that panels are delivered in 4′ wide panels, rather than 8′.  8′ panels can be moved by a couple of guys, but lifting and maneuvering them is difficult.  Each panel needs to be nailed to the next one every 2″ along the seam on each side of the panel.  It’s easy to nail one side, but flipping 8′ wide panels that way a few hundred pounds is difficult.

At any rate, we have a few new photos.  This is Hank, he’s our lead on site.  To cantiliver the roof over the entry (having a covered entry is nice in Portland), we were required to run thick beams (paralams) between the panels.  The roof is designed to carry the weight of an eco roof which requires the added strength of the beams.

Here is the roof deck, above the entry.  To get the panels to fit together, we are strapping them on each side and ratcheting them together, then nailing them on the top and bottom.  After several panels are fastened together, the final connection requires a good old sledgehammer.

Here is a shot of the kitchen.  It’s a little damp at the moment, but you can start to get a feel for the depth of the vertical volume and the amount of light that will be available.  The right side of the photo is essentially a glass wall, but is filled in at the moment with OSB panels for job site security until the windows are installed.  You can see a few pieces of conduit coming out of the slab.  These bring services to both the islands in the kitchen.

Lastly - this window opening has been our bane so far.  Our idea is to capture the view of the tree through the corner of the living room.  This window will be butt glazed together at the corner, and will be flush with siding on the exterior.  To make this happen, we need a steel frame to adhere the window to.  We couldn’t get the welder to show up to the site until the rain subsided.  The interior drywall will run straight into the glass without any trim.  It will appear from both the interior and the exterior there is no window in the corner at all.  I’m certain the finished product will have been well worth the wait!

Election day.

In the spirit of Election Day, we found this cool Google Gadget to track the votes as they come in:

Performance of the mini-split heat pump system

How efficient is our mini-split ductless heat pump compared to other heat pumps and other systems? This is a bit on the technical side but some people may be interested.

We are using a Fujitsu Halcyon 18RLQ which has a Heating Seasonal Performance Factor (HSPF) of 10 compared to the federal minimum requirement of 7.7. HSPF is the most commonly used measure of the heating efficiency of heat pumps. An HSPF >= 9.0 is considered high efficiency and worthy of a US Energy Tax Credit. (HSPF is calculated by taking the total annual heating requirements, including all energy inputs (defrost and back-up heating energy included) divided by the total electric power used.)

On the cooling side, the Fujitsu Halcyon 18RLQ has a Seasonal Energy Efficiency Rating (SEER) of 19. According to the product brochure, this provides an almost a 60% increase in efficiency over conventional units which just meet the federal minimum requirement of SEER 13.

By the way, there are several other manufacturers who make products with equivalent performance. We just happened to choose the Fujitsu.

If you’re wondering about site vs. source energy here’s my understanding of it. Our mini-split unit has a COP of about 3.5. Assuming the worst-case scenario in the Northwest in which the electricity is all coming from a 30% efficient coal plant (and even deducting 10% for transmission and distribution losses), it’s still more efficient than the most efficient gas furnace on a BTUH basis.

A better scenario is to take the natural gas you would use in a very high 95% efficient home furnace and instead ship it to the utility’s 60% efficient combined cycle gas turbine. With a COP of 3.5 (and 10% T&D losses) the overall efficiency is still almost 200% — twice as high as the gas furnace option.

Mini Split heat pump

We had a meeting this past week to discuss the final heat pump system we’re going to go with.  Ecotope did a great job designing and specifying a system for us.  The subcontractor on our job is also very knowledgeable and had some great points for us to ponder.  After about 1/2 hour of discussion, we had a system twice the size of what we started with.  Luckily, Jeff Pratt, our ‘resident’ expert who has very graciously donated his time and knowledge to us pointed out the big picture goal of the project.  We have designed the house to use less of everything.  The house is sited in a way to minimize it’s energy needs.  We have a 24′ tall vent stack right in the middle of the house.  With the extreme tightness and super insulated value of the envelope, whatever system we choose will rarely - if at all - be needed.  So the question wasn’t how large the system needed to be, but rather how small.

I’m certainly not an expert in this…in fact, probably not the best person to be writing this post - but I was excited to share this bit of information that I learned.  Because these systems are so efficient and do such a great job running at variable speeds, a system that can dip down into the 3,000 BTU/h range is what we need.  The subcontractor was arguing that a larger unit, 36,000 BTU/h would be great for cooling.  While this may be true, we’ve designed the house to not need the cooling.  The only reason we have cooling at all is because cooling is automatically included with the heat pump.  The larger unit also starts heating in the 8k range.  Because our heat load is in the 1k range, the large unit would kick on at it’s minimum, overheat the house in a mater of minutes, then shut off.  It was interesting to see how quickly our subcontractor changed his mind when he realized the best system in our house is the minimal system, not the maximal.

Updated framing photos…

We’ve managed to make a little progress framing over the past couple of days.  I mentioned in an earlier post I’d try to capture the magnitude of the shear panel nailing that is required with the panels.  Here is an image:

nail-therapy

As part of our commitment of reusing building materials as much as possible, we’ve managed to salvage some posts from a local deconstruction company.  While this may seem a cost effective approach, the post  was twisted and needed to be shaved and ‘trued’ in order to fit.  I’m guessing this isn’t a less expensive approach than buying a new post, on the other hand, we didn’t need to cut down any of our beloved doug fir trees to make the post.

We’ve been waiting a long time to get the framing on the roof so we can get a feel for the value of the roof deck.  We designed the house to sit very low on the site - both to be less intrusive on the site, and to allow southern light to reach the lower level of the house to the south of us.  One of the benefits we get from this design move is a flat roof on the front half of our house.  The cost of a flat roof - building up the roof crickets, and purchasing and installing the roof membrane is certainly more than a sloped roof, but for the money spent to add high quality space to a house, a flat roof is a bargain as far as I’m concerned.  With many older homes in Portland selling in the $300 per s.f. range, I’d guess our roof deck finished will cost 1/4 of that.  Our roof deck will get southwestern light most of year…it’ll be exciting to hear how the buyers of the house use the deck.

We’ll have more pictures next week.  We’re pushing hard to get the roof on and buttoned up before we see a lot of rain.

Barn wood and days gone by….

Our cartage driver, Mike, went to pick up our barn wood siding (see previous post) today. Turns out, when he was younger he used to move hay into the barn. We know the barn was torn down several years ago…he said the barn used to be beautiful.  Judging by the long 2″ thick pieces of Douglas Fir, I would agree.So what does this mean? It means Mike is an older dude.

more framing…

As we continue buttoning up the framing, we are moving forward on other items.  The windows from Marvin are ready to be delivered to the site.  We started picking up the barn wood siding.  The cor-ten steel panels have arrived and are sitting off site in storage.

We have realized some difficult details using the SIPs panels that weren’t necessarily foreseen.  For instance, many of the panels are shear panels, made to resist lateral forces.  To make the panels behave as designed, we need to nail them every 2″ around the entire perimeter of the panel….I’ll try and get a good image posted.  Also, we have heavy threaded rod that runs from the top of some of the panels, through the panel and bolts to the foundation to resist uplift.  Seems fairly simple, until you realize a 20′ long piece of threaded rod weighs a couple hundred pounds and is very awkward to carry.

At any rate - a couple framing pictures for the moment.

SIPs framing

As we stumble upon the weekend, I thought I would post a couple more shots framing shots.  We did our best during the design phase to focus windows in strategic location….this was done firstly to provide the maximum amount of privacy so window treatments wouldn’t be necessary.  Secondly, to focus views on landscape features such as trees.  Here is a view focused on a neighboring tree.

This next image will be a corner window in the living room with no vertical joint - butt glazed together framing a view of another tree:

of course we’re proud of our lumber (not that we’re using very much of it):

This is sort of an overall shot looking from the living room into the kitchen area.  The steel beam helps support the second floor cantilever.  floor framing for the second floor will begin next week:

MINI-SPLIT DUCTLESS HEAT PUMP

This is the heating/cooling system we are using in our project. They are relatively new in the U.S. but millions have been installed in Europe and Asia. It is a completely proven technology that offers substantial advantages over both gas furnaces and standard heat pumps. The name tells a lot of the story:

“Mini” refers to the size of the units which are generally smaller than comparable heat pumps.

“Split” because (like standard heat pumps) there is an outdoor condensing unit that is split apart from the indoor fan coils.

“Ductless” because…they are. This is the big technical difference. In mini-splits, refrigerant is piped directly from the outdoor unit through small-diameter insulated refrigerant lines. It goes to an individual evaporator unit and air handler mounted in the room that you’re cooling or heating. A quiet fan blows the indoor air across the cooled or heated coil and then directly into the room. With a conventional heat pump, the refrigerant lines run from the outdoor condensing unit to a central indoor evaporator coil, where the air is heated or cooled. The conditioned air is then distributed through ductwork branched off to various rooms. Since mini-splits have no ducts, all the hot or cold air they produce stays in the areas where it is wanted. Ducts (used in any type of central forced air system) are almost always run through unconditioned space such as attics and crawlspaces and they are rarely well designed, connected, insulated or sealed. The result is that in a typical house up to 30% of the hot or cool air that goes into the ducts ends up outdoors rather than in the house. There are a lot of better ways to design a heating/cooling system and the mini-split ductless heat pump is one of them.

I’ll talk performance and how they compare to other systems in my next post.

SIPs framing update

We’ve been cranking away at framing with the panels.  The learning curve was a little steeper than we had planned on, but we’ve hit our stride and things are clipping along nicely.  Here are a couple of images showing some of the tricky items we’ve worked through integrated the SIPs panels and steel framing.