It occurred to me that we haven’t really written a good post dedicated to vented rain screen assemblies. A rain screen is basically a gap created in between the sheathing of a house and the exterior cladding. It is considered by most building experts to be the most durable method of building an exterior wall and almost all commercial cladding details implement some type of a rainscreen. We have decided to use a vented rain screen on all of our Postgreen Homes and will talk about what we have learned to date in more detail below.

Benefits of a Vented Rain Screen

There are a couple of key benefits to using a vented rain screen assembly on any building that improve the performance and durability over the life of that building. Let’s put them in list form.

1. Equalized pressure means less air infiltration inside your building. Since there is an air gap between the exterior sheathing and cladding, the pressure is equalized with the exterior atmosphere. I’m no scientist, but basically this means that air is not going to be fighting hard to enter your building when it hits the cladding because the rain screen has eliminated the large pressure difference that usually exists between the exterior and interior of the home and various layers in between. This helps when you are trying to build homes as air tight as we are in order to achieve maximum energy efficiency.
2. Water the makes it past the cladding will drain and dry out, keeping the guts of your walls dry. This is where the durability claims come from. Water will eventually make it through any and all cladding assemblies on a building. The vented rain screen makes sure that when water does get through it is able to drain down the face of the Water Resistive Barrier and out the bottom or simply dry out on its own due to the air gap behind the cladding. This not only helps to keep moisture from getting into your walls assembly (which is bad), but it prolongs the life of whatever cladding is used by allowing it to dry out when wet from both sides.
3. An extra layer of air keeps your building cooler. In most homes, the sun hits your cladding which is in direct contact with the sheathing. The heat from the sun is transferred directly from the cladding into your walls. This makes your building warmer than necessary. The air gap created by a rain screen keeps the face of your sheathing much cooler. This is more important in the South where cooling loads dominate heating loads, but it’s still a nice feature in the north.

How to Build a Vented Rain Screen

There are many other people on the interwebs that I have linked to below that have described the how-to’s of rain screen building, so I’ll keep this brief. Here are the basic elements of any vented rain screen assembly:

1. Furring strips or a Drainage mat to create the air gap in between your sheathing/WRB and your exterior cladding. We list options for this material below, including our new favorite, The Furring Master!



2. An insect barrier at the bottom of the rain screen assembly gap with proper mechanical flashing. You want to keep the bugs from nesting in your rain screen from the bottom and water from draining into your basement.



3. A path for air to flow at the top of your cladding assembly. If you seal the top of your cladding to your roof cap or top trim piece, the rain screen is compromised by insufficient air flow from top to bottom.



4. A bit of extra care and planning at all window and door openings in terms of proper flashing. A good designer or flashing expert can help out here, but there are many details online for this as well that are simple to follow if planned for.

Material options for implementing Vented Rain Screens

There are many simple material options for creating the vital gap needed to build a vented rain screen system in residential buildings. There are much fancier systems implemented in commercial construction that we are no going to get into here. Some of the choices and their pros and cons are listed below:

• Pressure treated lumber – This option is one of the most popular as it is a familiar material, readily available and not too expensive. Rips of pressure treated plywood can be used or 1x material. This is what we used on the Passive Project. The main drawbacks are that the wood is not consistently flat and straight for precise cladding applications and water can be trapped between the wooden strips and the WRB with no room for venting where all strips are located.
• Mesh ventilation product – There are many mesh products available that are thin and easily applied in roll form over your WRB with a slap stapler. These products work great and eliminate the problem of trapped moisture completely that occurs with wooden furring strips. The main cons are the price and the uneven compression that can result in wavy cladding when fasteners are attached with different pressures. This is the product we used on the 100K House.
• Metal furring strips (The Furring Master) – Metal furring strips are our current favorite option due to a number of factors. The price is much better than the mesh products and not that higher than wood, depending on what type of wood strip you are using. They are perfectly straight and rigid which lends itself to the best finished installation of siding. One of our favorite aspects of it is that it has a hollow channel behind it that allows water and air to flow behind the surface, unlike wood. Lastly, it’s made of galvanized 22 gauge steel that is recyclable and can be left exposed in certain joints if desired without concern for UV degradation, decay or rusting.



Above is a picture of our installed Furring Master strips. We have studs at 24″ on center on the Skinny Project, but we installed the furring strips at 12″ centers. The strips in the middle that are not connected to studs are basically just maintaining the spacing from the wall and keeping the somewhat fragile panels rigid and secure.

• Miscellaneous other products – Although less common, we’ve seen others use creative products like corrugated plastic, rigid insulation and fiber cement strips.

Better links to Vented Rain Screen Instructions

Best post on Rainscreens ever by the BUILDblog – Fantastic diagrams and pictures from guys who really know what they are doing.

Green Home Building’s take on Rain Screens (PDF) – Good info, details and lots of hose wrap bashing. What more could you ask for?

Rain Control in Buildings by Building Science Corp – All sorts of good info about how rain and wind are trying to destroy your building and how to prevent them from succeeding.

]]> http://www.100khouse.com/2010/05/14/the-vented-rain-screen-via-furring-master/feed/ 22 http://www.100khouse.com/2010/04/14/postgreen-triplex-conceptual-rendering/ http://www.100khouse.com/2010/04/14/postgreen-triplex-conceptual-rendering/#comments Wed, 14 Apr 2010 15:23:40 +0000 Nic Darling http://www.100khouse.com/?p=1813

We have taken a look at the potential floor plans for the proposed Triplex, and I have told you about the zoning meeting going on tonight. Now it’s time to share a snapshot of what this thing might look like should we build it.

Some explanation:

1. The siding will be fiber cement cut into two foot strips and hung horizontally.
2. The colors will definitely be different then those pictured as we want to set this building apart from the 100k project which can be seen in the left side of this image. We just don’t know exactly what those colors will be so . . .
3. The tall window in the middle follows the shared stair tower up through all three floors. We have some interesting air sealing and insulation ideas regarding that tower.
4. The roof will be devoted to solar and other mechanicals. This means no roof access, but we make up for that by including the utilities in the rent.
5. The entrance (and this may be obvious) is below the tall vertical window on a small street directly behind the 100k project.
6. At the far end of the block you can just make out the train line that we think more than justifies the increased density of this project.
7. I kind of hope to live here.

Questions, concerns and compliments can be shared in the comments.

As we approach groundbreaking (pray for a good concrete pouring day), we have continued work on the Skinny Project’s distinguishing feature . . . House Tattoos. The strategy for the tattoos remains very similar to what was discussed in Brian Phillips recent post, but we have made some considerable changes to the content. The goal is a move toward more abstraction and hopefully a design less attached to a specific time or place.

Whatever design we eventually settle upon will still be executed by the artist and silk screening guru Candy Depew. She will print the design on our fiber cement panels which will then likely be clear coated to protect the work. We plan to document her progress so be sure to stay tuned for plenty of pictures and videos.

Below are a few recent design ideas that we like. Take a look and let us know what you think. We need to make a final decision in the next week, and your input would be greatly appreciated.

As usual, I have my favorite, but I’ll keep it to myself until the readers have spoken. Let us know which design you think should be featured on our next three homes.

Do it in the comments.

(Editors Note: Brian Phillips is the principle at Interface Studio Architects (ISA), the designers of our Postgreen Homes line. We are occasionally able to guilt him into writing a post.)

A big part of the fun of working with Postgreen is finding design opportunities within the tight parameters of budget, constructability and time constraints.  Simplicity has been at the root of much of our design process.  A key example of this elemental approach was established with the original 100K House in the decision to limit the exterior cladding to a single material.

By using only two colors of fiber cement panels we created a vertically proportioned, pixellated, urban camouflaged facade (as seen above). The M&M House and Passive House use horizontal fiber cement planks of varied widths and a painting strategy of different colored stripes adds variety to the otherwise simple exterior. (pictured below)

Our latest variant on this approach has come to be known as the “Tattoo House”.  The combination of flat cladding and paint has inspired a full-blown graphic strategy which explores the application of images to individual 2’ x 8’ fiber cement panels as seen in this early rendering of the Skinny Project.

We’ve been working with local Philadelphia silkscreen artist Candy Depew to develop a method for the application of these unique architectural graphics.  Candy and her team will print on the panels using large format screens with up to 4 colors.  (Before installation the printed panels will be clear coated to ensure resilience through the remainder of the construction process and to prevent long-term color fading.)

Pixel Strategy

In studying how to develop these house “tattoos” we’ve created a standardized approach for translating graphics — potentially from a variety of artists and sources — into a straightforward format for the 2’x8’ panels.

Panel Strategy

Our graphic investigation focused on how to crop existing images and patterns, the size of the images in relationship to the size of the house, and how to use color in a particular way that compliments the pattern and range of scale.

Crop Strategy

Color Strategy

It seems plausible that in the future Postgreen customers might be able to upload raster images and have them appear on their homes.  More excitement to come!

Click on any of the images to see larger versions on our Flickr page and please let us know what you think in the comments.

After the expected construction delays and difficulties associated with a standard as ambitious as Passive House, the Passive Project is finally getting wrapped up. Drywall is up, finish work is underway, and we are finally getting a look at the backlog of blog posts we owe you on this process. They are coming.

The most noticeable change at the site has been the exterior. Paint is on and other than some detail work at the base of the homes and the addition of our window shades, the outside of the houses are finished. So, for those that don’t attend to our Flickr page regularly, here are some of the images of the facades in all their glory.

So, how did we get here? How did these facades reach this particular point? This may be good time for a history lesson, or to be less pedagogical, a retrospective.

Some of you may remember the beginning of the Passive House facades. The early designs (pictured below) featured a variety of different materials.

We eventually moved away from these ideas due to the complexity of construction and the difficulty of working with multiple materials. From the discussions around revisions with ISA we reached the concept of single material facades (in this case fiber cement lap siding) as a design element. This thinking led to the lap siding version of the home, initially rendered like this . . .

From there color was added to give a sense of depth and excitement.

This addition received mixed reactions and was eventually toned down to this, our actual homes.

So, what do you think? Use the comments for praise, biting critique, partially formed emotional outpourings, worshipful haiku or any other expression of your feelings.

The 100k house and its neighbor, the somewhat erroneously named 120k, are moving briskly toward the finish line. The build, while a definite success, has been an education for everyone involved. We have learned dozens of valuable lessons about almost every aspect of our buildings, lessons we will soon be sharing with all of you, but for now we are going to begin to answer a bigger question: What are we going to do with all this new knowledge?

The simple answer to this question is the title of this blog entry . . . Postgreen Homes. We are beginning to move forward with our plan to insidiously spread our homes throughout Philadelphia (and beyond?). Like a sustainable, beneficial virus we hope to infect this city with more and more homes that are healthy, energy efficient and well designed. To this end we are looking for land, partnering in potential projects and developing options for our homes. The latter is today’s topic of discussion.

We want to build many homes over the next few years, but even we don’t want them all to look exactly like the 100k. We also don’t want our homes to serve only one type of lifestyle and living situation. While remaining within the definition of our brand, we hope to broaden our appearance and appeal. To this end, we have worked with ISA to begin developing a range of facades and floor plans that we hope will make Postgreen Home’s accessible to a wider audience.

Facades

Brian Phillips from ISA often talks about the importance of limitations in the design process. Our homes are all about creating within distinct and difficult boundaries like cost, LEED, Passive House, urban infill and size. These boundaries focus the design efforts and seem to be yielding excellent results. So, in an effort to make him regret his many words on the subject we suggested an additional boundary for the facade design . . . one material. Take that architect.

Well, he definitely took it, and he ran with it. I think you’ll agree that each of these three designs does an excellent job matching material to design and manages plenty of action within strict limits.

The Pixel

This is the facade you all know and many of you love. It is the face of our first Postgreen Homes in the 100k House project. We are very happy with the way its turned out and look forward to more incarnations in the future.

Material: 4×8 James Hardie Panels cut to 2×8
Color Options: Two colors from Hardie’s extensive line.

The Pixel facade option also lends itself well to a future dream we are tentatively calling House Tattoos. How would you ink your house?

The Tiger

This is the facade that will soon take shape on the Passive Project. The rendering is currently in gray scale but there is plenty of room for colorful experimentation.

Material: James Hardie Lap Siding in three widths.
Color Options: Two colors from Hardie’s extensive line.

The Brickasaurus
(An awful name created to spur suggestions in the comments. Tell us what to call this!)

This facade is not currently attached to a specific project though it is getting tossed around as a possible facade for several. Think of it as our concession to Philly’s obsession with brick.

Material: Thin Brick (probably)
Color Options: Two color choices from a surprising variety of options.

Seriously, think of a new name for this one or Chad might convince me to call it Sir Bricks Alot.

Floor Plans

Another area where we want to add some variety within the modest dimensions of our brand is in the floor plan and program of the house. We want to provide models that appeal to a slightly broader cross section of people and make this type of living more accessible to other lifestyles. So far we have three basic models, but like the facade options, you can expect that number to grow.

Forgive the tone of the descriptions, but for the sake of time I reused some more “advertisey” descriptions I already had around.

WORK

Designed for the artist, the entrepreneur, the entertainer or anyone who has always wanted to comfortably skateboard in their own house, WORK offers the extremes in space usage. One floor is a modest, comfortable living space and the other is a wide open place to work, play or party.

Options: Choose which floor you want open and whether or not you need the optional utility sink.

LOFT

Based on the original 100k model, LOFT is the essence of urban living. The open floor plan has an obvious disdain for doors and a flair for dramatic open space. This is the house’s answer to the condo. Loft living without the fees.

Options: Most of the options in this plan are probably going to be related to storage.

FAMILY

FAMILY understands that having a kid or two should not necessarily signify the end of your happenin’ urban lifestyle. A few doors to allow the young folks some sleep and an extra bathroom for emergency situations convert the loft concept into a family friendly environment.  Healthy, socially responsible living for you and yours.

Options: The downstairs bathroom will likely be an option. There will also be some storage options.

So there you have it. The beginning of our customization options and a peek at the direction of our future projects. Now its time for you to give us some feedback (and a better name for Brickasaurus). Get in those comments and tell us what you like and don’t like. Give us a lead on other facade materials you might like to see. Tell us which floor plan fits your life.

Comments GO!

We officially decided to go with the Pella Proline aluminum-clad wood casement windows for the 100K House project. The discussion that was sparked in the recent post on thermal shades was the clincher for us.

The Pella offering offered the best balance of modern style, quality, economy and energy efficiency for the home. The higher end brands as far as energy efficiency were just to far out of our budget to be considered in the end. The lower end offerings such as vinyl were also not at all appealing to us from both a green and design perspective.

Pella offers a nice look with aluminum cladding on the exterior in a nice range of modern colors and wooden interiors. The energy performance is good with U values of 0.34 for the operable versions and 0.29 for the fixed versions. We will actually have a number of fixed units in the homes, so the average U value will be around 0.32 for the home. The sliding doors from Pella that we selected also have a U value of 0.33 which is better than I expected.

I searched for a good image to show of the windows but just couldn’t find one of the specific model and style that we are going with. Most of the images show a more traditional window with grilles in between the panes. In case anyone is interested in the full details on Pella’s Proline windows, follow this link to their architectural design manual.

For the past few weeks the team has been kicking around the idea of an affordable green wall or green facade in the back of the homes. Yesterday, ISA forwarded me a bit of research on various methods for accomplishing a green facade using ivy for what seems to be a very low cost.

Green facades differ a bit from panelized “living wall” systems that incorporate pre-vegetated panels containing plants into the building envelope. The term “green facade” refers to a training structure that supports vines or climbing plants growing up from the ground away from the building wall (not directly attached like a living wall). Most facade greening systems use either welded wire fencing or stainless steel cables that climbing plants will grow along. ISA found this article by George Irwin (www.agreenroof.com) on green walls and roofs that goes into a bit more detail on the types of green walls.

Of the cable and welded wire systems, I think we are leaning more towards the wire mesh. We should be able to find a roll of galvanized wire mesh similar to what is shown here for under $200 that will cover the entire rear facade of the 100k house. We will simply need to fasten the mesh in such a way that it stands a few inches away from the facade and then we can cut openings around the windows to keep the vines from growing over the windows.

This method is modeled after a more robust and expensive green wall system offered commercially by a company called greenscreen that offers an array of systems for creating attached and free standing green walls. The image below shows one of their installations that is similar to the effect we will be going for on our facade.

We are very pleased to find that this type of green facade can be created in a low-tech and low-cost manner that can be afforded on our modest budget. This should add both a beautiful architectural/landscaping element to the home while also keeping the home a few degrees cooler during the summer months.

Other interesting links on green facades and living walls:

• Institute of Physics in Berlin Green Facade
• Green facade using wire rope (translated from German)
• Wall Creeper Wire Systems from Anzor
• Vertical Gardens by Patrick Blanc

I noticed today that it’s been a while since I’ve posted any pretty pics so here are the latest renderings from ISA. We have been discussing how to create an interesting, modern and affordable facade for weeks and this is what we’ve gravitated towards.

You can see that we have a bit of a vertical theme here. We are showing James Hardie Vertical Siding Panels cut to two foot widths in a few shades of gray. There is also some very light gray stucco on the facade of the 100k house in the background that will will most likely put on the rear of both homes as well. The windows are now all in vertical orientation as well to fit in with the 2′ widths of the Hardie siding.

ISA is still experimenting with possible picture windows on the second floor of the back of each home or some type of contrasting horizontal window element. They are also looking into how we might be able to incorporate a down and dirty green wall of ivy over the entire rear facade that is Southwest facing. This would further passively cool the home in the summer while providing a unique green element to set the home apart (I guess it’s set apart quite a bit already).

I’m really happy with the new renderings and really can’t wait to see it come to life. We are still checking with the Hardie reps and investigating ways to make the install as easy as possible. We’ve all heard horror stories about how difficult vertical Hardie can be to install and we hope to simplify the process to keep labor costs low.

ISA and I have had a few meetings since the discussions on the new floorplans last week. If you look closely you will notice that we have incorporated some reader suggestions such as surrounding the new bathroom layout with closet space rather than having them run the length of the side wall. Special thanks to David for this suggestion.

The kitchen and ground floor layout have been debated the most. In the current plans we have a sleek island or peninsula with all of the bulky appliances and storage hidden under the stairs. We have made a few sketches where the stairway and the storage and cabinetry below it are made into one piece that is disconnected from the wall an upper level. If we can’t pull this off design or budget wise then we will most likely look at keeping the peninsular where it is and adding the bulky storage along the opposite wall of the stairs to make a simpler L-shaped kitchen. This will leave the plan open and flexible while making the task of sourcing affordable cabinetry much easier.

The elevations show a mixture of stucco and James Hardi siding mounted vertical in strips of varying widths. I like the “light mist” color a lot which is basically a light grey. We talked about painting a few random strips with a different color for an interesting and cheap effect. We have some more research to do on the labor involved with mounting the siding in different configurations as well as how we can handle the edges and corners without making the home look too traditional.