Insulated Pre-Cast Concrete Panels: Strength and Security of Concrete with Additional Thermal Perfomance!

What do you imagine when you think of a concrete building? Is it a tall sky scraper? Or do you picture exposed concrete in your living room? The materials architects and builders have been using for millennia have hardly changed. Other than the use of steel, we are surrounded by timber and concrete buildings.This is for good reason, timber and concrete are excellent building materials. But in the past few decades, engineers and designers have asked, how can we build it better?

Questions like this led to building materials such as pre-cast concrete slabs and glue-laminated beams. These materials meant that we could build bigger buildings and do it faster. Pre-cast concrete slabs are panels that are formed off site, in accurate molds by highly skilled experts and then shipped to the site. From there the panels could be tilted up or hung into place with a crane and group of skilled workers. Producing panels in a controlled environment, there was no need for form works to be built or extra cement mixing trucks to deliver and spread concrete, productivity sky rocketed. Despite the huge advantages of pre-cast concrete, we have to ask, can we build it better?

Retrieved from: www.wright.ie/product/customised-wall-panels/

Enter insulated pre-cast concrete panels. These composites are made up of 2 concrete panels called Wythes, separated by a layer of rigid insulation in between them. The wythes are usually anywhere from 2.5” to 6” in thickness and are held together using one of various forms of connection systems such as a carbon fiber truss or plastic pins. Different R-values are achieved by increasing the depth of the insulation between the wythes and can range from R-5 to R-50 (Handorf, 2012). It is important to note that great consideration is needed when considering which type of connection system to use. One of the major benefits of using these panels is they can create a complete building envelope. This includes the weather barrier, moisture barrier, insulation, and even the interior finish (Handorf, 2012). Because of this, choosing a connection type with high conductivity can reduce the effectiveness of the insulating membrane. Nonetheless, concrete is a well known excellent thermal mass. Concrete can absorb energy, hold that energy, and release it slowly. Further insulting that mass can result in positive gains and reduced loads on HVAC systems. If designed well, insulated pre-fab concrete panels can reduce peak HVAC loads and allow for a smaller system to be installed.

Retrieved From: www.wright.ie/product/insulated-wall-panels/

Unlike tilt up pre cast concrete, pre-cast insulated panels are made to order and delivered “just in time” to the site via truck. The panels are then set into place with a small crane depending on the scale of the project, and relatively small ground crew of 4-6 people. This not only saves time on raising walls as rotating, positioning and then tilting up a panel is labor intensive. But, there is also no need for any formwork to be built and torn down. There is no time waiting for the concrete to set. When a panel arrives, it is ready to be put up! Another detail that can be easily overlooked is how this can affect a construction crew progress. With all the panels being manufactured off site, weather does not become an issue as far as casting goes. And with the ability to act as a complete building envelope, time and energy can be saved by the lack of need for multiple sub-contractors to complete the building skin. Insulated pre-cast concrete composites are also very strong! A panel with 4” of insulation between two 2” wythes will behave structurally the same as a simple 8” solid panel. The difference of course is that a structure made with insulated concrete panels will reduce the need for extra insulation or cladding to the exterior of a building. Adding to the versatility of these systems is the fact that they can be used as structural elements creating an entire shell, or can replace structural elements such as cast in place columns. Maintenance of this building system is very minimal. Concrete is known to have a very long life span. Only requiring the occasional cleaning as desired, and maintenance of water proofing systems such as caulked joints and drainage systems. 

Just like technology and cars, our buildings are getting smarter. We expect more from them and we expect them to operate at a certain level of performance and comfort. They are becoming more efficient, the technology and new building methods that allows for these improvements is very exciting, but familiar. With this re-imagined form of concrete, we can create very energy efficient buildings in ways that previous builders couldn't. The production of concrete itself is one of the largest green house gas emitters into the atmosphere. By taking little steps to increase efficiency where ever we can, we can not only make better homes for our clients and friends, but a better place to call home for all of us as well. 

Footnote:

Handorf, Chris Von. (2012, December, 21). Precast Insulated Wall Panels: Get the Whole Package! [Blog Post]. Retrieved from: https://precast.org/2012/12/precast-insulated-wall-panels-get-the-whole-package/

A Brief Introduction to CLT: An Environmentally Conscious Alternative To Concrete

1. What is CLT?
CLT is an exciting, new to the USA, engineered mass timber product that was recognized by the International Building Code in 2015. It stands for Cross-Laminated Timber, it is a structural member that acts similar to pre-cast concrete panels. Unlike pre-cast concrete panels however, which produce a large amount of carbon emissions during production and in the form of off-gasing during setting, CLT is produced from renewable tree farms. Energy is needed to produce engineered timber products, but unlike concrete after it sets, CLT sequesters carbon in its lifespan up to 50 years. 

2. Why is CLT exciting?

While the mantle of being first in Washington has been taken, CLT projects are nonetheless very exciting in the architecture world. CLT projects in the US are very rare, and students like myself would and are studying them with a forensic level of detail because of the huge potential they show for the future of sustainable architecture. 

Retrieved from: www.thinkwood.com. (2013). The CLT Handbook. https://www.thinkwood.com/products-and-systems/clt-handbook

2. What, if any, are concerns regarding code restrictions, energy requirements, and cost/affordability?

According to the city of Seattle building code section 2303.1.3, CLT may be used in accordance with ANSI/APA PRG 320. This allows for type III, type IV to be built up to 4 stories, type V-A to 3 stories, and type V-B to 2 stories. A simulation cost model using 2 different panel thickness’s for walls and floors established an average production cost of $19.20 per cubic foot. The simulation and write up about procedures can be seen in the “CLT Handbook” by Think Wood, which is free to download from their website. 

The cost benefits of using CLT for a single family home would not be as dramatic as the gains seen in mid rise buildings. The cost of material is comparable to light weight framing, however the benefits become more noticeable during construction. Pre-manufactured panels are delivered to the site via truck, and can be lifted into place with a small crane and grand crew. Less people are needed to build a frame, and all openings are cut out with CNC precision for doors and fenestrations. 

Over the lifetime of the house, the efficiency of having a tight building envelope and the thermal efficiency of CLT walls will add up for big savings as well. 

4. Are there any energy or thermal comfort benefits of using CLT?

Just as pre-cast concrete has enough mass to absorb heat energy and hold onto it to release later, so to does CLT. CLT floors can have a concrete subfloor with radiant heat to further take advantage of the density of the timber. CLT is made completely off site and specific to each project. Each piece is CNC routed to extreme precisions. As a result even just the shell can be made to be near air-tight without extra materials. This extra control of air leaks saves energy and can produce a noticeable positive difference to savings over a year. 

The most noticeable gains are seen in during construction. All design elements that are specified to be CLT panels are made off site like pre-cast concrete and are delivered “just in time”. When a CLT panel arrives on site it is made to fit and immediately ready to be set. Placing CLT panel can be done with a small ground crew of only a few people and a small crane that can easily fit into residential sites. 

CLT construction needs a considerably smaller crew to construct CLT framing. Retrieved from: inhabitat.com/jesse-garlicks-sky-house-is-an-off-the-grid-vacation-retreat-in-washington/sky-house-washington-lead/

5. What are typical design considerations to take into account when designing with CLT?

CLT panels are pressed into long panels that are then cut to a specified shape and size. These panels are anywhere from 7’-15’ in width, and can go up to 24’-60’ in length. These panels can also very in depth via number of ply’s per panel. These range from 3-ply, 3.75”-4.25” in depth to 9-ply 9”-12.5” in depth per panel. Typically, 3-ply panels are used for wall sections, and 5-ply are used for floor and roof sections. Moisture control is an important with CLT as it can absorb a high quantities of water, but has a low permeability. As a result water takes much longer to evaporate from the shell than if it penetrated a typical light frame structure. 

CLT panels are not very dense. Because of this vibration and sound transmittance control is important to consider. While it is possible to build an entire residence out of CLT, for interior walls sometimes it is more appropriate to use conventional light timber framing for cost benefits. CLT panels have a relatively low sound transmission class, for areas that are known to make a lot of noise would require extra sound deadening resulting in thicker walls than usual. If saving every square inch is a priority, than CLT might not be appropriate. But thick walls can be utilized as expressive architectural feature showing strength in its mass.

6. Why should I consider using CLT?

It is this authors professional opinion that as CLT becomes more recognized it will gain popularity very quickly. I was in school when CLT was first being brought to the US, it was well received from my professors and cohort alike. Timber has always been an excellent building product but it was very limiting in how it could be used. Compare to concrete or steel which can be molded in any form or welded into place. The benefits of off site production, precision machining, “just in time” delivery to site,  and ease of construction means engineered timber is competitive alternative to traditional building methods

CLT can be a wonderful exposed deign feature as well. Retrieved from: inhabitat.com/jesse-garlicks-sky-house-is-an-off-the-grid-vacation-retreat-in-washington/sky-house-washington-lead/

Footnote:

-www.thinkwood.com. (2013). The CLT Handbook. Retrieved from https://www.thinkwood.com/products-and-systems/clt-handbook

Wants Vs. Needs: Tips for Your New Home

    Building a new home? It’s exciting stuff I know! However along with all of the excitement and fun that comes with designing and building your new home, is the initial nitty gritty detail of site and lot selection. It may sound like a minor aspect, but in reality it’s a major first step to your overall home building process. I’m going to share with you 6 key components for you to keep in mind throughout.

   Wants vs. Needs

1. Your Priorities

    Remember this new home belongs to you, so it’s very important that before you go scoping out potential locations to figure out what you really want to gain from the location. Is your commute going to be an important factor? Or would you rather have amazing site views from your new home? Go through your particular lifestyle and decide what exactly is a must, and what things could fall a bit further down the wish list.

2. Site Evaluation / Current Conditions

    Once you’ve determined what features are most important to you and you’ve begun looking at locations, be sure to really evaluate the site for what it is. Look at the current conditions of the land and note how much upkeep it would initially require to bring the lot up to your standards. Note what kind of native vegetation is there, considering if there are any rare plants or animals in the area.

3. Zoning / Buildable Area

    Zoning is actually a big deal in this business. It’s crucial to know what exactly comes with your piece of land and being aware of the rules and regulations that come with it. You wouldn’t want to accidentally overreach into your potential neighbors or city property. That often leads to future headaches dealing with legal matters, so to avoid any mishap it’s always best to know what belongs to your land and what you’re allowed to do with it. Also knowing what your buildable area on your site is major. There are codes and setback laws that essentially set up rules for how much you can legally build on your site. Getting familiar with those initial conditions is a huge benefit, prior to purchasing the property. 

4. The S’s: Slope, Sun, and Soil

    Slope is a critical piece of information in any building project. The steeper the slope, the costlier it will be to construct on it. There are so many things to consider, especially cost which comes hand in hand with how well the site will play with your design. Building a safe structure should be the first priority in any design build project, therefore being certain that the slope of the selected site is capable of building your newly designed home. Sun exposure is a huge component in every design. By considering the sun angles of your site will help enhance your gains from the design. Your new home is designed to either keep heat in or out depending on the time of year, so by analyzing those angles, it could really help cut costs on your heating and cooling bills throughout the coming years. An energy efficient home has many benefits but they all come from how well your design and utilize the opportunities presented with your site. Soil conditions of your site is another driving factor of construction cost. Whether your new house will rest on a bed of soft dirt or hard rock, preparing that land for future construction is a costly process. In addition, you want to design a drainage system that is strong enough to handle the water runoff on the existing soil. Scoping out these details are a crucial part of selecting your building site.

5. Outlook for Future Growth

    When considering building locations for your future home, think about your selected neighborhood. Are there any good school districts? What businesses prosper here? What’s this area going to look like 5 years time? Are there solid opportunities for future growth? These aspects will all affect your cost and overall value of your future home.

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Let's Talk Mini [houses]

Architecture is complicated. One would think that you could simply dream up some crazy design and plop it on a land, but often times that is not the case. Designs are driven by so many elements - the land, the codes, the weather, etc. But isn't that what makes the 'problem' so fun to solve? 

Jim's initial notebook sketches. From the beginning, we knew we  would need to bury the house into the ground in order to achieve multiple floors with the city's height restriction. 

One of our recent projects came with a very unique 'problem'...... a plot of land that is only 25' wide. You might be thinking, "well, 25' is still pretty wide!", and that is very true. Unfortunately, there are city codes (laws) in place that turn that 25' into 15' wide build-able area. A 15' wide space is not very large to fit all of the spaces of a modern day home, especially if you want to squeeze in three bedrooms! Adjusting the plans to have one continuous path of circulation on the eastern side of the house allowed more space for bedrooms, while also bringing lots of daylight into the hallways. 

North and South elevations showing 'pop-out' boxes that were added to maximize square footage on the small lot. We really took advantage of every bit of city code to make the most of the land! 

On top of the minimal width of the land, there was also a very short height restriction on the plot - just 18'! We knew from the beginning we would need to bury the house in order to create multiple stories. We took this as yet another challenge. Why not make the most of the so-called 'basement'. As seen below, we decided to dig out the majority of the lower level to create a garden room. Although buried, the space feels light and gets plenty of sunshine - with the added bonus of lush landscape all around! 

East Elevation showing the buried house with the dug out land. Quite the opposite of a basement!

I guess the moral of the story is - sometimes the most difficult of problems are the most fun to solve! Your land may direct the design, but there is always a solution! While these were early sketches, the design concepts stayed intact throughout the process. If you want, feel free to go drive by the house under construction! Here is the address:

4843 South Lucile Street, Seattle, WA 98118

Feel free to share your thoughts!

Environmentally Friendly Architecture

Look out! There is a new wave of environmentally friendly materials being produced!

As a team, we at Castanes are always on the lookout for sustainable and earth-friendly materials to be integrated into our projects. From geo-thermal heated flooring to solar paneled roofing, we enjoy the opportunity to introduce sustainable products and processes into the world of residential architecture! 

We recently came across a new material being used as flooring and walls- Cross Laminated Timber (CLT). To give you a brief understanding, the Engineered Wood Association defines CLT as, "a large-scale, prefabricated, solid engineered wood panel." So, what does that actually mean?? The timber is cut into 2x4s, laid together, and alternates directions each layer. See the image above to get a better picture!

What does all of this 'archi-talk' mean for you?? It means our taller mid-rise - and potentially even high-rise, buildings can be made using wood instead of concrete or steel! Crazy, right? Not only are the CLT panels as strong as concrete and steel, they are a renewable resource. The panels are also faster to construct and can be sourced locally, so all of you owners and developers out there can probably already here the 'cha-ching!' in your pockets. 

We'll be posting on a more regular basis, so feel free to give our blog a follow if you would like to stay up to date with us!

The New York Times Feature of The Sanctuary House

Castanes Architects has been featured in The New York Times for the second time!! The article covers one of our more recent projects, The Sanctuary House. This contemporary hillside residence embraces the unique bay of the Puget Sound with dynamic views and "inner" courtyards. 

Our Smith Tower Apartment goes viral!

Our Smith Tower Apartment was recently featured on Evening Magazine. NBC picked up the video and is broadcasting it nationally. It now has more than 3,000,000 views and is being called "the coolest apartment you've ever seen!". We certainly think it is! Before Petra and her kids moved in, the space was nothing but unused storage. In 2000, we fully transformed the tower into a magical place to experience urban living. Take a peek inside! 

VIDEO LINK: Click HERE

NOW OR NEVER.

On December 15th, 2015, Councilman Tom Rasmussen held a meeting at the Seattle city council chambers to discuss the concept of 'lidding' Interstate-5! A lid would reconnect the surrounding neighborhoods that were divided when the interstate was constructed, as well as create space for the community. the meeting covered the costs, resources, and overall possibilities. Emphasis was placed on the urgency of beginning this conversation now, while the Convention Center addition is going through its beginning design phases. Below is the concept vision of where the lid will be located. 

Image by The Northwest Urbanist at https://thenorthwesturbanist.com/2014/07/05/lets-bury-i-5-redux/

Please read Scott Bonjukian's, one of the speakers at today's meeting, article HERE for more information on the Lid concept, as well as examples from other cities.