Air Sealing: Step 01

Intello-Plus on the interior of our walls.

This is the first of what I think will be at least a couple of posts on our Air-Sealing strategy for the house. Air-Sealing is one of the most important parts of the our energy-efficiency strategy: without proper air-sealing, all our fancy super-insulation and passive-solar heating wouldn't make a lick of difference. We'd just take all that nice conditioned air and throw it away, as cold air seeped in through the cracks. 

This house is totally sealed on the interior and uses a Zender HRV (a Heat Recovery Ventilator) to move air into and out of the house. We used a similar Zehnder unit last summer on the Solar Decathlon project and were very happy with how easy it was to install and set up. So we'll give it a shot again. But HVAC is a post for another time. Right now its all about Air-Sealing!

To let people survive inside a house you need a certain amount of 'fresh' air (for  . . . you know: breathing). Also, you want to take all the smelly bathroom, kitchen and 'stale' air and send it outside - (but again - heat recovery and ventilation is another post)

In a 'normal' house, this fresh air just comes in through cracks in the walls, around the windows, under the doors and lots of other places. But the new cabin uses a machine (the HRV) to, in a controlled way, bring this fresh air into the house and take the stale air away. The thing is, this machine can only work well if the rest of the house doesn't let the air move through cracks, windows, doors and . . . well: you get it. 

In addition keeping the warm indoor air in - its super important NOT to let this humid indoor air come into contact with anything cold (like the exterior siding of the house) otherwise it will condense and we'll be in serious danger of rot, mold, insects and all the other nasty things that water does to a house.

So: we Air-Seal!

Parsons-Stevens Solar 2011 Decathlon: Taping the seams of OSB panels that line the walls and ceiling of the house

There are lots of ways to air-seal a house. But the most important things are to make it continuous, simple to install, and durable. One way we've tried in the past is to use OSB sheathing on the interoir sides of the walls and floors as the air-barrier. Once the seams between OSB panels are taped, it forms a pretty good - very durable air-barrier. The problem is it isn't very easy to install and, depending on where you locate it in the wall - it can get in the way of things like electric, plumbing, insulation and all the other good things that are supposed to live inside the walls. Above you can see Siga tape being applied to interior OSB. I found this method difficult mostly because of how it affects the building process, not really for any detailing reason. You end up sealing up chunks of the wall too early in the build for air-sealing reasons, and there just isn't quite enough flexibility for my tast - though it is certainly super durable.

The Pro-Clima Intello Plus Membrane. Its all in German so you know it must be good.

So this time around we decided to try the Pro-Clima Intello-Plus membrane for an air-barrier. One of the nice things about NYC these days is the huge community of folks interested in this type of building: we were very lucky to have the folks from 475 High Performance Building Supply right down the street from our office and the guys there were super helpful in detailing and spec'ing this system. 

The Intello-membrane is a sheet that we'll be installing on the (warm) interior side of all our walls and the under-side of the cathedral ceiling. This membrane is not only our air-barrier, but also serves as our vapor-retarder, and the netting for when we blow in cellulose insulation. So three-in-one: not bad. 

Below you can see a diagram of where the air-barrier is located in our wall assembly: inside the structural member, but under the finish layers. Note it connects to the subfloor OSB which we'll tape to form a full seal all around. 

SO: run the membrane, tape all the seams, and tape the plywood subfloor seams: thats the strategy. We'll see how it works out on site.

While we aren't anywhere near ready for running the membrane just yet (we're still in the 'rough' part of rough-framing) - we did have to prepare a couple of areas to accept a good air-seal later on. Its important to think through all the air-sealing details long before construction starts so things can be prepared accordingly. 

One area that requires a little prep is where we have interior partition walls intersecting our exterior (air-sealed) walls. Once these walls are joined we won't be able to run the membrane as easily - so everywhere this occurs we decided to run a strip of membrane behind the partition wall which will allow us to easily tape the membrane later. 

A strip of the Intello Membrane where the partition wall will intersect the exterior wall

Now that the membrane sticks out 6" on either side, it will make taping to it later on much easier. 

Similarly, today we started installing a ledger board for all of our second floor joists to hang off, and so we had to run a strip behind this ledger board all the way around the house.

Carrie cutting membrane strips to go behind the ledger board.

installing the membrane with staples - on the left you can see the ledger board being installed over the membrane. 

All of this will hopefully make things easier and more effective when it comes time to actually install the full membrane. While we could have taped to the ledger and the partitions (instead of slipping behind), we thought running strips of membrane would actually be easier and a better detail in the end. 

So far the Intello has performed great. Its already lived through a couple FIERCE wisconsin summer storms, and I have to say the Pro-Clima tape sticks like nothing I've ever seen before. So, so far so good. This is only the first step though, and things get really interesting around windows and doors - so look for that post soon.

Jason, entry porch framing

House Framing, the Digital way

Framing is rolling along well. We've got all the main walls up and the interior partitions went in the other day. We've got second floor materials being delivered tomorrow and then up we go!

Carrie framing out one of the big windows

Jason working on the interior of the double-stud walls

While I have lots of good photos of framing I'd love to post, I thought I'd take some time and talk about the digital design process we used while designing the framing a bit first though. We used a digital 'Building Information Modeling' (BIM) software package to design and document the house and we are trying to use this software to manage our information as much as possible. 

The full BIM model of our little cabin

While I like working in the BIM world and there are a lot of nice documentation tools in the product we're working with, I'm especially interested in the capacities of the tools to streamline and manage the crazy amounts of information in a project (even one as small as a little cabin). In parallel with large-scale design decisions, we used the software to sort of 'pre-build' the structure - allowing us to make all (we hope!) our mistakes in the digital model first and streamline the building process.

Column and Beam 3D model

As part of this - we developed a comprehensive framing model of every piece of the house. While this is overkill for most projects and not exactly 'built-in' to the software - we were able to turn it into a pretty good  framing management tool. 

(Disclaimer - some of the following is going to be a bit nerdy) We started by creating our own suite of families within the structural discipline for all our framing members, including columns, LVL and steel beams, studs, headers, sills, etc. These families were created to allow us to manage information like count, cut length, ordered unit length, placement and phase, etc. The main structure includes lots of engineered-lumber columns and beams - we set up special filters to allow us to isolate elements within the software to facilitate viewing and management. 

The full framing model with all the studs, rafters, joists, etc.

The above image is of the full framing model. We modeled as much as we could - the colors correspond to different 'phases' of the build so we can easily see what's going on and where. By going through the process of digitally framing the house we were definitely able to work out some of the more complicated areas. This model then feeds directly into the framing plans we have been using on-site to build the project. Below is a screen-grab of the framing plan and you can see we've worked out corners, Rough-Openings and all the relevant dimensions ahead of time. This is super useful to us since we knew we'd be the ones building this thing so it made sense to try and work out as as much as possible ahead of time. By also fully modeling the plumbing and HVAC system as well we are able to identify conflicts and modify the structure way before anybody is down in the basement hacking out chunks of important beams so they can run their ducts (Yes - that does happen!)

Close up of the first floor framing plan

While all this visualization and modeling is great and fun - its not really anything that can't be done with good-ol' pen and paper. The real exciting thing is the shot below!

Yes - I know, it looks like a spreadsheet - and it is. But to those of us in the construction management world this is gold. Because of how we built the framing-member families we are able to itemize and record all the material that goes into the final building. There is all sorts of good stuff here: Counts (of course), where and for what the member is used for (Headers, sills, studs, etc), and best of all cut-lengths and ordered unit length. The category for 'Is Nested' allows us to take the small pieces (short cripples, sills) and nest them in large pieces of lumber. This way we can be super efficient with our material ordering (especially important for us cus' we're out on a special project and don't have a shop to store extra material or anything like that). This info is accessible on-site so when someone asks: "Why are there so many 2x6's" we know exactly what they are for. 

Close up of framing keys and schedules

All the members have unique identifiers as well and so we have a series of 'Key-plans' showing locations and schedule info of every piece of wood that goes into the building. While I know there are lots of wood-framing specific programs out there that can kind of do this for us - I really like the flexibility and control allowed by building our own system. And, of course, control is what its all about. 

I hope that wasn't too wonky for you - and for those of you who just want to see pictures of us building stuff, don't worry - there's lots more to come soon. 

Floor Framing and the First Walls Going Up

Monday Morning - the foundation is finally ready to go.

We finished up all the site and foundation work last week - and that means we were finally able to get to the fun part of framing the house! This is always the most dramatic part of building a house, and by thursday we had some walls standing and you could start to see the house taking shape. 

But first we had to get the floor and basement walls all framed up (as well as take some time and finish the garage roof). 

Below you can see the main carrying beams and basement walls going in. The basement is only 6' deep because the water table is so high this close to the lake - so its more of a crawl-space than a real basement, but it'll still work for storage space. The wood framing you can see in the center is the main mechanical space - this is the only part of the basement that will be conditioned and part of the house's insulation envelope - the concrete slab in this part is isolated from the rest and has thick foam insulation around and under it. 

Basement concrete walls and wood interior walls. The big beams will support the main floor joists.

Jason cutting LVL's for the floor beams

One element of this home which makes it very unique is the insulation and air-sealing detailing we are executing.  Part of this strategy includes continuously insulating all the Wall sill (bottom) and head (top)  connections. So where the main floor, wall and foundation all come together was a place we worked hard at to make as insulated as possible. The strategy we decided on was that by thickening the foundation walls, we are able to land the floor joists on the interior edge, and then sit our wall on the outside of the concrete wall. We can then add insulation all the way around the Rim joist very easily and eliminate all thermal bridging of the floor framing (thermal bridging is when heat is transfered along the framing member and lost to the outdoors)

The extra thick foundation walls - the floor sits on one edge and the exterior wall extended past it to add insulation - the concrete block here will be the finished exterior and sits on a shelf cast into the foundation walls. 

A Typical Sill detail - the exterior wall of the double stud framing overlaps the floor deck - totally insulating the Rim Joist - the steel angle is actually just concrete in the final build

While this detail ads a tiny bit of cost (the extra concrete) and complexity, we actually found it very simple to build and didn't have any difficulties with it. There is a bit more layout and attention that needs to be paid to things like stud length, but the comprehensive digital framing model we built worked great to allow us to pull those kind of dimensions right out of the digital model. We modified the detail a bit on site by eliminating the steel angle and adding a shelf directly to the concrete foundation wall - this simplified things even further. This shelf supports two rows of concrete block which will be a nicer looking finish than the raw concrete. 

By thursday morning we were ready to stand some walls up! One of the extra nice things about our double-stud wall is that it is made of two 2x4 walls set apart. This means we can build out of nice light, inexpensive 2x4s and the wall framing went real quick.

Jason, Carrie and John framing up the first walls!

By noon we had walls standing up. The main floor wall height is 10' - with a lower area under the loft. These big walls have square 5'x5' windows punched through them which are huge! The view looks great and will be very dramatic. Below you can see the southeast corner looking towards the lake. 

I've been back east in Massachusetts since thursday afternoon - but I'm heading back to the site now and I'm excited to see how the gang did over the weekend. This week will be lots more wall framing and maybe even getting into the roof if things go real well. 

One of the big 5'x5' windows in the first wall.

Oh - and also, I started a new Instagram account  - so if you like, please follow me and I'll be posting lots of pics there as well as we keep building. just search for ed_p_may

Wisconsin: First Weeks

Its been a week and half of Wisconsin now, and the house is coming along well and we're all having a great time. We're staying in little cabins right near the building site: each one is a unique little character of its own. Its been a great week of BBQs, Fish-Frys, kayaking on the lake and getting ourselves acquainted with our summer diggs. Ohh . . . and some house building too in between all the eating.

We've got foundations all in, and this week we spent a few days framing up the nearby garage so we'll have a nice dry place to store materials and work in from now on. It was also real good to stretch our framing muscles after a whole winter of sitting around doing computer work.

The house foundation at the entry  - you can see some of the lake behind as well

But since there isn't very much dramatic to show on the house just yet, I thought I'd talk a little about the house design and show you what we'll be spending the summer building. 

Main Floor Plan showing Living, Kitchen, Entry and Bedroom

The plan of the house is pretty simple and includes about 1200sf of main floor space with another 600sf or so in loft above. The family uses the house as a winter gathering point during holidays and such, so lots of kitchen and ample living room was pretty much a given. This cabin is replacing a much older cabin which used to occupy the same site until it sadly burned down in a forest fire a short time ago. Like that original cabin, this one has a single bedroom and also lots of loft sleeping space for kids and guests. Unlike that original cabin - this one utilizes very sophisticated construction technology to create a warm, airtight interior environment. 

Interior View showing Kitchen Island and wood finishes

Here you can see a proposal for some of the interior finishes and organization. The kitchen is embedded in a thick 'core' which supports the loft above and contains a large bathroom inside. The Island spills out into the living space and will have (we hope) concrete countertops that we'll be making on-site, as well as Walnut cabinets to contrast with the White-Pine wall and ceiling cladding. We're trying to find something a little smoother and tighter than the traditional 'knotty-pine', but still playing with that aesthetic and material that the clients enjoy so much. Dark metal fixtures and railings will add some texture and a finner-grain than the thick wood walls and core.

The main house shape and organization is driven by many (sometimes competing) desires and ideas. First is the client's memories of the original cabin and their fondness for many of the lost elements; things like large gable windows, a high level of transparency from lots of windows, and a warm wood feeling throughout. 

This region features many log-homes built in a slightly different style than the traditional linkin-log we're familiar with. These vertical log cabins use logs held together standing up to form the main house envelope, with the logs often cut flat on one side to create the interior finish. The log-cabin is, of course, a very labor intensive building type, and simple forms lend themselves to this technique both because it saves labor, but also because in the cold winters a compact shape is much easier to heat than a large, rambling home. 

For this project, a simple gable form was oriented to maximize lake views to the north, while also providing views of a nearby bay to the south and east, and of course allowing for lots of passive solar heating.

Once the main house shape was established and the interior organization was mostly figured out, we slightly 'tweaked' it to better conform to the site and shield the interior spaces from a nearby neighbor to increase privacy. This also better oriented the 'face' of the house (the gable end) towards where you will drive onto the site, giving you a great view of the big windows and covered entry.

Finally, the 'mass' of the house was 'carved' into to create covered entry and porch spaces. This 'removal' of chunks of the house is expressed through material changes at these areas, the dark siding becoming a light yellow color and some of the columns bursting through the envelope to expose themselves. On the south side, a large deck was added which will get lots of use during the summer months. 

The coming week will see us starting on the main floor framing and then moving on upwards from there. So lots more pics to come soon.