We just settled on the Two Point Five Beta yesterday marking the completion of Postgreen’s eighth house. We don’t have final photography or LEED results yet, so this is just a quick celebratory post with a more comprehensive one to follow.

This house is the first to feature our new 1two5 Cabinets in the kitchen. The Sepviva Line, designed with matte laminates, aluminum edge banding and clean, simple lines was created for this house in Matte White and Terril. It features the Frigidaire slide in hybrid induction range and the Whirlpool/Bosch combo of fridge and dishwasher. The dishwasher blends in with a custom door panel. The final piece is a 2cm Ceaserstone countertop. We snapped some quick scouting pictures of this kitchen the other day with young Teague in the role of professional model. We felt his former work as an unhappy hipster qualified him for the work. Here’s a sample. More will follow when we take the actual professional shots.

In addition to the 1two5 kitchen the Two Point Five is home to another first. It is the first time we have beat the Passive House air sealing requirement of .6 ACH (Air Changes per Hour) at 50 Pa. Our final blower door came in at .54 ACH as you might have guessed from the cryptic title of this post. We will have more discussion of that in the coming week including how we got there and how it effects our final HERS rating.

Well, it’s a somewhat brief and unsatisfying post, but I promise more very soon. For now, feel free to put any appropriate unhappy hipster captions for the above picture in the comments. Check out the real site for inspiration.

As we build the Skinny Project, we are taking care with all of our air sealing details and making notes on possible changes to reduce labor and complexity in all future homes. One of the key notes I picked up at last year’s Passive House Conference was that those who had been actually building these homes for a number of years were all stressing multiple layers of defense against pesky air infiltration. I thought I’d throw out a quick post to give the basics of our current multi-layer approach at sealing the movement of that crafty air thing that is so prevalent on our planet from sucking the heat out of or into our homes:

1. ZIP System sheathing with all seams taped with butyl tape.
2. Combination of gaskets and sealant sealing all critical rough framing connections.
3. Dense Packed cellulose insulation.
4. Drywall gaskets or continuous sealant along all corners, top/bottom plates and window/door openings.
5. Locate outlets in the floors and use wireless light switches to eliminate all drywall penetrations in the walls.

More details and diagrams to come as we improve our construction docs for Awesome Town.

We thought it would be a good idea to review our new ventilation strategy and design implemented in the recent Passive Project. The ventilation strategy in the 100K House was different than most typical houses and the Passive Project took things a step further. We’ll start with the outline:

1. Use a very efficient mechanical ventilation system (ERV or HRV >90% efficient)
2. Design an efficient duct run layout to maximize efficiency of your ventilation system
3. Eliminate all dedicated local exhaust systems ducted directly outside
4. Eliminate all dedicated appliance exhausts that are ducted directly outside

High Efficiency Mechanical Ventilation (ERV or HRV)

The Passive House standard requires that you install a ventilation system with > 75% efficiency and a low electric consumption of 0.45 Wh/m3. When we say ventilation system, we are talking about either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). HRV’s exchange heat only while ERV’s exchange both heat and humidity.

A 75% efficient unit will be exchanging 75% of the heat from the indoor air with the cold air coming inside. The closer that figure is to 100%, the closer the fresh, incoming air will be to the existing indoor temperature. Efficient electrical consumption is basically referring to the type of motor used in the ventilator. European models typically are using the most efficient DC motors available, while unit made in the US will suck a bit more power.

If you are shopping the globe, you have a couple of options for mechanical ventilation that meet the Passive House reqs. If you want to buy in the US, you have one choice – The UltimateAir RecoupAerator.  This bad boy comes in black, runs at 95% efficiency and sucks a paltry 40 Watts while delivering 70 cfm to your home (250W @ 200cfm). This is what we spec’ed on 100K and continue to use in Passive and for all foreseeable projects in the future. We set it on its lowest setting which usually measures about 60cfm in each room vent and let it run 24/7/365. Simple.

This unit also comes standard with a MERV 12 filter which gains us LEED points and keeps our client’s air very clean. Lastly, it features an “EconoCool” feature that can be used during the summer to reduce cooling loads. Flick this switch on and the unit will recognize when the temp drops below 65 degrees F and automatically shut off the energy recovery and begin swooshing that cool night air directly into your bedroom.

Maximize Efficiency with a Well Designed Duct Layout

Now that we’ve got the correct ERV for our needs, we need to pay attention to how we run our ductwork to maximize efficiency. The ERV will suck out stale air from the home and deliver fresh air to rooms at the same time. Below is how our PHIUS consultants recommended that we locate our suckers and blowers (technical Postgreen terms):

Stale Air Exhausts (Suckers)

• Bathrooms
• Kitchen
• Near Washer/Dryer

Fresh Air Inlets (Blowers)

• Bedrooms
• Living Room

Now we don’t just want to throw the ductwork in any old pattern to get to these rooms. We want to minimize 90′s and have straight runs as much as possible. Basically a 90 degree turn is equivalent in resistance to airflow as 25′ of straight duct and a 90 degree register termination can add as much as 80′ to your calcs. The main pointers given by both PHIUS and the manufacturer of the UltimatAir are as follows:

1. Keep it SHORT
2. Keep it STRAIGHT
3. Keep it SMOOTH
4. Test after the system is commissioned

The diagram above is a 3D layout of our proposed duct runs for the Skinny Project. Laying these out in Sketchup is pretty quick and helps us really think about how each duct run needs to get to it’s final destination with the fewest turns. As a result of this exercise we added another small chase wall next to one of the closets in an upstairs bedroom. This chase will not be seen, and could be considered a minor detail, but it will greatly improve our duct efficiency and reduce labor time for our installers.

Other tips given to us for optimal ERV system performance:

1. Always use smooth, hard duct and avoid flexible duct as much as possible.
2. Insulate the two lengths of duct running between the exterior and the ERV. This will prevent condensation from forming on these lengths of ducts.
3. If noise is a concern, add one 3′ section of insulated flex duct to the supply side of the ERV. Install this section as straight as possible and it will act as a silencer without needed to buy an expensive silencing duct section.

Eliminate Dedicated Local Exhaust

The big difference between the 100K and Passive ventilation strategies was increasing the amount of intakes/exhausts inside and eliminating the local exhausts in the bathroom and kitchen. PHIUS highly recommends doing away with any local exhaust that is basically sucking conditioned air directly out of the homes and replacing it with whatever outdoor air can be sucked through any cracks in your envelope. Eliminating the local exhausts also reduces your exterior penetrations through the envelope by at least two (more if you have more than one bathroom).

To compensate for the lack of dedicated local exhausts, we install suckers in the bathrooms and kitchen. On top of that, we throw an ERV boost switch in each of these rooms so that occupants can boost the ERV fan to max setting (around 200 cfm for UltimateAir) while they are in use. These switches are also useful for parties or times when a lot of CO2 producing bodies are inhabiting your space.

In the future we plan to take this boost switch a step further by linking it directly to the bath lights with an auto shutoff delay. Basically when you turn on your bath light, the ERV will automatically boost to high. When you leave the bath and turn off the light, the ERV will remain on boost for another 10-20 minutes to fully clear out any fumes you may have generated during your visit. This gets us a LEED point also.

Eliminate Exhausts for All Appliances

This is less of a ventilation system design aspect and more of a whole house envelope and mechanical design strategy, but I like to include it here as well for good measure. By using electric water heating backup for our solar thermal and a condensing dryer that does not require venting, we have eliminated all appliance ducting to the outside. Less thermal bridging and warm air being sucked out of our homes. To compensate, we locate a sucker near the condensing dryer that can tend to get a little steamy at times. In the future designs, the washer/dryer is moved into the bathroom to allow the bath sucker to serve two functions.

That’s it. I hope this helps with any mechanical designs you may be considering for your next green building project. Comments are below.

One last note:
One question we still get a lot is if our homes are too tight and cause indoor air quality problems or pressure balance issues that would cause the windows and doors difficulty in opening and closing. This is a bit of an outdated concern from when production builders first started making their homes tighter without adding mechanical ventilation. Now, this issue is a thing of the past unless you have a very poor builder…

Yesterday we looked at some lessons learned from our aggressive air sealing goals on the Passive Project. In doing so we mentioned that we will be utilizing building gaskets and air sealing tape to help obtain the very difficult building air tightness goal of 0.6 ACH @ 50Pa that is required by the Passive House standard. Let’s take a more detailed look at the technology and economics of these two construction materials that are less than standard in the average US home.

Building Gaskets vs. Construction Adhesive

Over in Germany where the Passive House standard originated, they have been using rubber building gaskets for over a decade rather than typical construction adhesive that is used in the US building industry. These gaskets are usually made of EPDM and are similar to the ones used in automotive applications. These gaskets offer a far superior seal for water and air infiltration in difficult and uneven joints like wood to concrete and even wood to wood connections.

I just stumbled on a company in Baltimore, MD – Conservation Technologies – that carries a whole host of these German inspired building gaskets, along with a whole bunch of other cool building products for earth loving projects. They have a whole list of reasons why their gaskets are better than caulk or foam that is typically used in the US. Below are the Pros and Cons that we see:

Pros of Building Gaskets

• Superior seal to caulk and foam gaskets or adhesives for both water and air infiltration, especially on uneven surfaces.
• Gaskets will last forever with no deterioration.
• The installation is easy to perform and easy to verify whereas caulk or smaller foam gaskets are very difficult to verify proper application once the walls are secured in place.

Cons of Building Gaskets

• Cost premium (see below for analysis)
• Limited availability
• Construction crew resistance to new technology that is clearly awesome and being used in the rest of the enlightened world for the past 10+ years.

Cost Analysis of Building Gaskets vs. Construction Adhesive

I’ve compared the raw material cost only of two applications of the gaskets. The first is a gasket that would go on a 2×4 to be used at a sill plate location or between the first and second floor of a house. The other is an interior application at the drywall to wood connections. It’s clear that the cost is 2-3 times that of conventional construction adhesive. Some may claim this is expensive, but I was happy to see that the cost difference was not much higher.

2×4 Building Gasket = $0.44 per linear foot
Double Construction Adhesive = $0.15 for two lines per linear foot (1/4″ beads with 10% waste per tube)

Drywall Building Gasket = $0.16 per linear foot
Single Construction Adhesive = $0.075 per linear foot (1/4″ bead with 10% waste)

If we were to take one of our standard building footprints of roughly 18′x40′ that would mean our perimeter is 116′. We would use at least three instances of the 2×4 gasket at the sill plate, second floor and roof details for a total of 348′. Using gaskets rather than a double bead of construction adhesive would add roughly $100 to our material costs. Not bad at all for extreme confidence in a good number of our critical air sealing junctions. Not bad at all.

Air Sealing Tape Analysis

OK, we’ve looked at gaskets, now lets look at using a whole bunch of tape to seal the seams in our sheathing prior to installing our WRB. This seems extreme to most, and maybe it is, but man does it look good. It also seals a building up really nicely for very little additional non-skilled labor. I mean, we can all handle a roll of tape.

Passive House people love this Grace Vycor Tape for their OSB air sealing. I’m sure there are many other butyl based tapes out there that are similar and just as effective, but we will use Grace Vycor for our example. It can be found online in 6″x75′ rolls for about $24 which is not cheap, but certainly is not a bad deal for such a lovely product.

Our homes are small and infill, so we have two facades that are roughly 18′x25′ to be taped. This equates to 900 square feet with roughly 12′ of tape needed for each 32 square foot sheet or sheating (only two sides need tape as the others will overlap other sheats). This gives us $337 of tape needed. Let’s go ahead and round that up to $500 for extra tape needed on corners, windows and door openings if we are so inclined. While this is more expensive than the gaskets, it’s still manageable and should go a very long way to reducing air infiltration in our homes.

So there you have it. For less than an extra $600 in material costs and negligible labor additions, we have created a very air tight envelope that is easy to inspect and verify. Your costs in detached homes will obviously be larger, but they should still be in line percentage wise with your build costs as you are already used to buying more sheathing, cladding and the like. Offer your thoughts on these material additions to traditional builds in the comments and thanks for reading.

It’s been a while since we posted on any technical aspects of the Passive House we are trying to build in the Passive Project. We recently tested our air sealing with a blower door test prior to drywall at the homes and I figured it would be a good time to bring up some thoughts on our current air sealing methods along with future ideas we plan to implement.

Last time we spoke about air sealing was when we looked at our foundation and slab insulation and under slab air sealing. Since then we have obviously finished framing, sheathing and cladding the homes. Let’s recap our basic air sealing strategy since these posts on the foundation.

Above Grade Air Sealing Techniques on the Passive Project

1. SIPs walls and roof – Review SIPs Construction Details and notice how much sealant they spec in the assembly of a SIPs building. This along with the SIPs themselves, makes for a much tighter home than an average stick built home. We improved our sealing details from experience gained on the 100K House installation.
2. The poly air barrier from beneath our slab was wrapped up inside the house and continuously taped to the interior of the SIPs walls to eliminate air leakage at the critical junction between slab, foundation wall and first floor framing.
3. A Tyvec air and water barrier was installed on the exterior of the walls. All seams were taped and all windows and doors were taped, caulked and foamed to the Tyvec barrier. Normally people don’t tape the seams. We made sure each seam was taped.
4. Tyvec was all used in between the homes at the party wall as seen in the image above. All seams were again taped, and this layer was wrapped around to the facades and to the roofing membrane to form a continuous barrier.
5. The typical rubber roof acts as our air barrier on the roof.
6. Each penetration through the slab or roof was taped and foamed to its surrounding air barrier with a detail similar to the one shown below.
7. A wireless electrical switch in combination with floor outlets along the interior facades of the homes, eliminates electrical penetrations through the SIPs walls.
8. All LVLs were designed not to penetrate any exterior walls to maintain the airtight SIPs walls.
9. All joists and rim boards were hung internally to make for a simpler and more airtight exterior wall construction.
10. All drywall is glued to the interior of SIPs and framing.

This is a long list and if I had to pick the most critical out of this, I’d say it is the SIPs, the under slab poly wrapping up to the SIPs and the envelope penetrations as the key details that are significantly different from normal construction. The Tyvec layer inbetween the two homes was also not the easiest sell to the construction crew.

We implemented all these items to the best of our ability, but mistakes were made along the way. It’s hard to tell where sealant or tape may not have been applied as needed. These omissions have resulted in a lower than desired tightness at our pre-drywall inspection. We’re not exactly sure of the actual result due to some HVAC and electrical openings that were not completely sealed at the time of the test, but we think we are somewhere in the range of 3-5 air changes per house at 50 Pascals of pressure. Our ultimate goal in the Passive House standard is 0.6 ACH @ 50Pa, so needless to say, we are doing our best to patch and caulk any and all air leaks that we found during the test.

The biggest lesson I’ve learned from both building the Passive Project and attending the recent Passive House Conference in Urbana, Il is that this 0.6 ACH @ 50Pa target is by far the hardest spec to achieve in the Passive House standard. I would say it’s even harder for a production builder to achieve in an environment that does not allow extra time and budget to fix some errors along the way. An owner/builder can decide to add another month or three and a couple grand to their budget to make air sealing changes on the fly. A production builder needs to have their plan bulletproof from the beginning and execute it to the T or the entire construction schedule and budget will be thrown out the window trying to recover.

Key Airtight Construction Lessons Learned

• Design multiple layers of air sealing. There should be one primary line of defense against air infiltration in your envelope assembly (A red line drawing), but you should not stop there. Take every opportunity to air seal anything you can from the outside to the inside of your walls and roofs. I have Mr. Hayden Robinson to thank for this advice at the Passive House conference. I was pleased to see him present on his latest Passive House design that looks almost identical to the planned construction on the Skinny Project.
• Design simple to implement air sealing details. If a crew is completely unfamiliar with a certain product or method, then sometimes it is best to re-think a detail. If everyone can understand the detail and believes it will be worthwhile to install, there is less chance of corners being cut when someone is not looking on the job site. Sometimes it is also better to spend more money on a better product that will reduce labor costs when time and budget are a concern.
• Design easy to inspect air sealing details. It is kind of common sense, but it makes sense that it is easier to require strict air sealing if it is easy for your forman to inspect the critical details during assembly and preferably after assembly. If a gap can be caught easily at the end of a daily inspection before it is covered up the next day, you’re going to end up with a much tighter house in the end for the least cost.
• Document your critical air sealing details well. This sounds logical, but most air sealing details can get lost in the mix when surrounded by many other structural and material details and callouts. We prefer to have specific diagrams on separate 8.5×11′s that can be made into a book to reference on the jobsite. These details get down to the very basics of the critical air sealing materials and junctions. They can also be blown up much larger than normal when placed on their own page.

OK, now that we’ve covered that, we can move on to what we are planning for the next project in terms of air sealing. As we have heard, we are going away from SIPs on the next project (dang, I need to post on why) so we have our work cut out for us.

Future Air Sealing Construction Strategies

1. Document each critical air sealing detail on it’s own 8.5 x 11″ page for easy reference at the construction site as stated above.
2. Tape all seams in exterior sheathing with Grace Vycor Tape.
3. Install an one way air tight Water Resistive Barrier (Tyvec, VaproShield…) and tape all seams over the sheathing.
4. Use Conservation Technology Building Gaskets at all critical wood to wood and wood to concrete connections while framing. I love these gaskets and will write an entire blog post later on why. They rock.
5. Apply construction adhesive liberally at all wood to wood connections near the exterior sheathing where gaskets are not used.
6. Install Conservation Techonology’s Drywall gaskets on interior framing to provide an airtight seal once drywall is applies without having to install costly poly or similar air sealing barrier.
7. Use rigid XPS insulation with taped seams as air barrier on basement walls that connects to sheathing above and underslab insulation and poly below.
8. Use specialized double sided butyl tape of window gaskets to seal around windows and doors in addition to spray foam. I haven’t made up my mind on the best method here. Gaskets are great and I think the tape is even better but only found in Europe right now.
9. Use Protecto Wrap’s Dual Guard Threshold Tape under all door thresholds. This is a nasty area where metal is usually meeting concrete and just doesn’t seal well.

Well, I think I’m spent on this post. I apologize for the lack of diagrams. They will follow hopefully in future posts. Please add to my lousy lessons and ideas in the comments below and I will try to participate as much as possible.

In addition to insulation levels and air sealing details, the windows and external window shading in the Passive Project is upgraded from the 100K House Project.

There is a lot more to windows than insulation levels, but in order to keep things simple we will focus on this aspect and cover energy efficient windows in more details in a future post. For windows, U-values are used that equate to the more recognized R-values used to define wall and roof insulation. The lower the U-value, the higher the R-value. In our region of the US, a U-value of 0.32 (R-3.1) is required to reach Energy Star status. Many are surprised at how low insulation values for energy efficient windows are compared to even the lowest R-19 code built wall.

In the 100K project, we used the bare minimum for Energy Star in a Jeld-Wen builder grade window. For the Passiv Project, we upgraded to the only US window manufacturer capable of meeting the specs required by the Passiv Haus standard, Serious Windows. Below is the comparison.

Energy Star: U 0.32 (R-3.1)

100K House: U 0.32 (R-3.1) Jeld-Wen Builder Grade Wood Clad Casement

Passive Project: U 0.17 (R-5.9) Serious Windows 925 Series

To further increase the overall window insulation in the Passive Project, we increased the amount of glazing % taken up by picture windows. The 925 serious of Serious Windows figures for picture windows increases to U 0.14 (R-7.1). Over 2/3′s of the glazing in the Passive House is comprised of these picture windows.

See the diagram below for a comparison of some of the leading window manufacturers in the US. Notice that Serious offers windows that achieve R values all the way up to R-11.2.

So how does Serious achieve these higher efficiency figures? Below is a diagram of how the Serious Windows are constructed. They start with their frames by using fiberglass which is a better insulator than any other window frame material commonly seen such as wood, aluminum and even vinyl. They then fill these frames completely with spray foam. There are a bunch of small energy saving features inside the windows, but the biggest difference with Serious is that they offer triple and even quadruple glazing. They save cost and weight by using suspended films rather than full sheets of glass for the layers inside the inner and outer most glass panes.

There is a lot more to cover on the subject of uber-efficient windows, but we’ll cut off this discussion for here. For those interested in cost difference, we spent just over double the amount on the Passive Project windows as we did on the 100K windows.

]]> http://www.100khouse.com/2009/09/11/super-efficient-windows-for-the-passive-project/feed/ 11 http://www.100khouse.com/2009/07/15/new-passive-project-page/ http://www.100khouse.com/2009/07/15/new-passive-project-page/#comments Wed, 15 Jul 2009 20:13:57 +0000 Chad Ludeman http://www.100khouse.com/?p=1118

The goal of the 100K House blog is to facilitate learning about sensible, green building on the interweb. So many times when we find a good project out there, little details are provided on the construction especially in one concise format. That’s where we are trying to fill the void with the 100K blog.

To that end we have just revamped our project page format with the new Passive Project Summary Page. The new page format gives a bunch of the overall details split up into different subjects. There are not a lot of posts on the Passive Project yet, but as we get more up, the most pertinent ones will be linked on this page as well. You will notice there are a few linked already.

All of this detail is followed up by a nice photo gallery of the project. Right now I just have this gallery displaying some of our photos from framing. When a project is completed, there could be a nice assortment of photos throughout construction as well as final photos and initial renderings.

Next will come the revamping of the 100K House Project page. This could take a bit longer as there could be a lot more posts linked from it. I may also just wait until we have done final summary posts of the 100K project.

Take a gander and let me know if you think we should add any more categories or details on this summary page. There is probably a couple day window that I will actually keep working on this thing until I shelve it for next year… If you are astute, you will also notice a series of ads and links to our new PostgreenHomes.com site at the bottom of the page. This is a work in progress that will be launched the 30th. At that time the links will be directed to specific pages on the new site.

Many have been waiting for us to start posting on specifics of our Passive Project which contains two homes – one of which is seeking the stringent Passive House certification for extreme energy efficiency. We have been waiting to post until we have completed each section of the build. This ensures that we post once on exactly what we ended up building rather than what we hope to build.

Now that we have finished pouring our foundation and have begun putting up our first SIPs panels, we can dig into the nitty gritty of our Passiv Haus construction details. Let’s start with the foundation wall/slab construction and insulation details.

Our Passive House consultants from PHIUS (Passive House Institute of the US) gave us the following basic design rules for our foundation and slab insulation:

1. Under slab insulation of R-50 (10″ of XPS Rigid insulation)
2. Outer foundation wall insulation of R-10 (2″ of XPS Rigid insulation)
3. Separation of the floating slab from all foundation walls with a minimum of 1″ (R-5) of rigid XPS Insulation

I’ll spare you the details, but we did not get to this design in one day. Once these reqs were finalized, we came up with our own version of how we would build the foundation and had it approved by PHIUS. Below are the three main types of foundation details we needed to cover. The standard foundation wall is how most of the perimeter of the foundation is built. The new party wall is the foundation wall in between the two new homes we are building. Finally, the existing party wall is the detail for the party wall next to the existing home on the site next to our Passive House.

Standard Passive House Foundation Wall Detail

Passive House New Party Wall Foundation Detail

Passive House Existing Party Wall Foundation Detail

There are some air sealing details in the above diagrams that we will talk about in more detail in another post coming up. The basic main issue that was difficult to pull off in our foundation, was ensuring that the slab was completely floating and isolated from the foundation walls with at least 1″ of rigid. Typically in Philly, the slabs will rest right on top of the foundation walls for extra support. In our case that would cause too much thermal bridging from the slab to the foundation.

Below are a few more pics of the actual construction.

We just realized that we have been uncharacteristically quiet about our next project. We are due to break ground in just a couple of weeks, and we have barely written a word about it. This is very unlike us, and I will begin to remedy the situation right now.

Our next project is similar in scale and ambition to the first. We will be building two homes, side-by-side, just a block and a half from the original 100k Site at the corner of Amber and Arizona (map). These two homes will share the original vision of providing healthy, energy efficient and professionally designed homes at a reasonable price. The corner home, known as the M&M House, is already under agreement, and our buyers, Mario and Mel, anxiously await its completion. The true infill home will go on the market when we break ground.

In an effort to continue improving our energy efficiency we will be pursuing the Passive House standard in this project. This is a German building standard that aims to reduce the heating and cooling load of a home by 90% (you may have read about it recently in the New York Times). We are working with PHIUS (Passive House Institute US) to finalize the design and get our Passive House certification. The process has been fairly smooth so far, and we think we have a great home in the works.

While we won’t be pursuing LEED Platinum on these two homes (one standard at a time), they will be built to the same or better standards. We will definitely return to LEED after this project, but we see the Passive House standard as a great way to improve some very specific aspects of our houses, mainly the envelope and the mechanical systems. In these two areas, Passive House far exceeds even the highest standards of LEED.

The goal, as always, is to pursue this new standard in an affordable manner. The infill home, which will act as the true case study for this project, will be a two bedroom, one bath, loft style row home (much like the 100k). The house will come in at about 1300 square feet. Our goal is to adhere to the same requirement as the 100k House project and build this home for less than $100 per square foot in hard construction costs. With any luck this will allow us to provide one of the most affordable Passive Homes ever built in the US.

We will be going into a lot more detail on this project as we go forward including talking about the new mechanical system, insulation, windows and other changes the new standard requires, but for now, I will leave you with a couple early concept sketches of the new facade.

So, what are your thoughts on the Passive House standard? Are there reasons more people aren’t pursuing this standard in the US? What do you think of the new facade concepts? What materials would you like to see forming this new facade (stucco, lap siding, metal)?

Show up in the comments.

Since studying the Passive House standard of energy efficient design, we have been trying to determine what we can incorporate into our project without blowing the budget. Below are some of the ideas we have so far to improve the energy efficiency of the home after consulting the Passive House Standard.

Insulation

1. Increase SIP wall panels to 6.5″ (R-25) thick from 4.5″ (R-17)
2. Increase SIP ceiling panels to 10.25″ (R-43) thick from 8.25″ (R-32)
3. Look into increasing insulation under the slab (currently ~R-14). If we keep our radiant heating system it may be beneficial to leave a hole in the insulation in the center of the slab in order to utilize the ground as a heat sink to maintain a more constant temperature in the slab. This needs further investigation.
4. Investigate ways to further reduce thermal bridging with SIPs manufacturer
5. Investigate whether we can afford bolstering the insulation of the walls on either side of the SIPs panels. A 1-2″ layer of foam board insulation on the exterior before the cladding is installed could boost our R-value by as much as 14 to bring us to R-39. A half inch of EPS foam board on the interior walls could replace drywall, adding another layer of insulation and allowing us to use an American Clay type of product to finish the walls that would also further improve the indoor air quality.
6. Investigate a radiant barrier layer under the roofing material and above the SIPs.

Efficient Windows

1. Investigate fiberglass windows with better U-values than the currently spec’ed Pella Proline series. See this window post for more info on options. Marvin Integrity is looking good right now as far as value but may still be a premium compared to the Pella’s.
2. Replace the existing spec’ed sliding glass door with an energy star rated model.

Mechanical Ventilation with Heat Recovery

1. Implement and HRV or ERV system as cost effectively as possible with minimal ducting.
2. Investigate the possibility of using earth cooling tubes under the foundation that feed the HRV/ERV that will pre-heat or pre-cool the incoming air naturally prior to entering the home. The main issue here is the fear of condensation building up inside of the tubes under ground that could lead to mold formation.
3. Investigate the possibility of incorporating a dehumidifying element into the HRV/ERV system that would allow us to eliminate a separate air conditioning system in the summer.

Efficient Heating System

1. Radiant heating still seems to be the best way to go for our home as we will not be able to reach the full passive house standards in all other categories that could allow us to use the HRV/ERV system only with a post heating element. We also really like radiant heat and think it will be a great feature of the home.
2. The heating source is still not nailed down as it depends on whether we will need air conditioning or not. If we do, then it may make sense to use a heat pump capable of cooling and heating the home and the water supply. If we do not need air conditioning then we will lean towards a gas, tankless unit with the option to add a solar thermal array.

As you can see, we don’t have all of the details nailed down yet. This will come in the next few weeks as we look at the budget in more detail and finalize the construction drawings. We may also look into hiring a consultant that is familiar with passive homes and efficient heating, cooling and ventilation systems for them.