KEC Week 12

The past few weeks the focus has been on foundations.  The East wing of the building has a full basement which will be used for mechanical and electrical rooms, laundry, and storage space.  The rest of the building foundation is a slab on grade with frost wall foundations.

 [ concrete crew laying out foundations, they "step" down at this corner to allow the Earth Duct to come under the slab]

To build the foundation you start with the footing.  Wooden forms are used to create the footings.  Sometimes reinforcing steel or rebar is required in the footings.  After the forms and rebar are installed, the concrete is placed in the footing.  When the concrete hardens, usually about a day later the forms are stripped and then the foundation walls are formed on top of the footing.  

[foundation wall in progress, some wall is complete while the foreground shows rebar in progress]

[ basement foundation wall in progress, that opening is for a louver into the mechanical room for fresh air ]

[ concrete crew working on basement foundation wall forms; in the foreground is the elevator pit]

[this is the NE corner of the building, near the new kitchen, the carpenter is installing a brick shelf that will support the stone veneer]

You usually start by building the outside formwork, then install the wall rebar, and then close up the wall by installing the inside formwork.  Then concrete is placed in the walls.  Often this is placed using a concrete pump truck.  Again, when the concrete hardens the forms are stripped and now the foundation is complete.   Since the basement is a finished space, it is important to properly waterproof the outside of the foundation walls, provide good drainage along the wall and away from the building, and provide insulation.  We will start this work in a couple of  weeks and I will discuss these methods in more detail at that time.

Where there is no basement we have frost walls.  The steps are generally the same, start with the footing and then build the wall.  The main difference is that this is only a frost wall which means you only go deep enough to prevent the effects of frost heaves in the winter when the ground freezes.  In New England this is typically between 3-1/2 and 4 feet deep.  Since there is no finished space behind the frost wall and the slab is on grade, waterproofing is not usually required on these walls, but it is still a good idea to use damproofing and insulation.

   

[here is the frost wall with just the outside forms up]

[here the frost wall has been closed with the inside forms up]

While the foundation work has been advancing, we have also started work on the site utilities.  We have connected the site storm drains, domestic water service, and sewer service to the town utilities in the road.

While all this activity is taking place on site there is also a lot of work in the office, pre-planning site activities.  Shop drawings are being prepared by the various subcontractors for the elevator, timber frame, mechanical equipment, and electrical equipment as well as coordination drawings locating all of the piping and ductwork below the slab, above the ceilings, and in the walls.  These shop drawings and coordination plans are reviewed by the design team and the Construction Manager to coordinate with the design and each other's work to ensure when all the materials arrive onsite they can be properly assembled without any issues.  This is a very critical part of the project that avoids issues on site which can lead to delays and costly changes.

@Home: Low VOC Paint

Everyone has heard the saying, "You can talk the talk, but can you walk the walk?"
It's real easy to read about building "green" and get excited about it at work and talk it up with clients, especially over the past few years where it has been such a buzz in the industry.  But when it comes to making changes in your own home, you have to ask yourself how willing are you to go ahead and try new things?  And if you aren't willing to try it yourself, then should you really be advising others to do so?
At home I've been picking off the low hanging fruit like adjusting thermostat set-points,  recycling at the local recycle center, changing incandescent lamps to compact fluorescents, using cold water and light load on the washer machine, and reducing length of showers to name a few.
This past weekend my wife and I decided to change the paint color in our daughters' bedroom.  We picked out colors from a Pottery Barn catalog and then went on-line to confirm products.  I was happily surprised to see that Pottery Barn recommends a Benjamin Moore product called Natura Zero-VOC Interior Paint.

I priced out some options and found Natura to be around $52 / gallon.  Another Zero-VOC option that Benjamin Moore offers is called Eco Spec and this was closer to $30 / gallon.  When I asked the paint dealer the difference he explained that the Natura provides better coverage as it is a higher quality paint.  This price range between a high quality product and a mid to low range product was typical for Zero-VOC, low-VOC, and standard paints alike.  And it is commonly stated that a more expensive paint is a higher quality paint which provides better coverage and can equal less coatings and therefore less labor.
So after weighing out a few options, I decided to go with the Natura and see if I noticed any real difference.  I picked up a gallon of primer and a gallon of eggshell and got to work.  It went on very smooth and even.  It dried fairly quick so I had to make sure to apply it evenly and finish an entire surface at once to avoid flashing or patches.  I did notice one significant difference - the lack of odor.  I was really amazed by this.  Quite often you may be in a room painting then you leave the room to get lunch or take a break and you come back in and you are hit with the odor that you didn't notice before because you were in the room.  Well there was almost no odor and this was really amazing.
I remember working on a project at the MFA in Boston and the museum curators required a period in our construction schedule for "off-gassing" which occurred after construction was complete and prior to the return of the artifacts.  This was my first museum project and I was unfamiliar with the term so the curator explained to me that the materials in the newly renovated space give off gases that are harmful to the artifacts and they needed a period of time for the highest concentrations to dissipate before they could safely bring the artifacts in.  I remember wondering if the fumes were so harmful to these artifacts, why wouldn't they also be harmful to people?  This was a few years before LEED became prevalent in construction projects.  But when LEED did come out I was happy to see an emphasis on flushing out the building prior to occupancy to protect the new occupants from odors and fumes from the new materials.
All in all, I was very happy with Natura and I felt good about the decision to use a Zero-VOC paint in my home, especially in my daughters' bedroom, and I would continue using this paint and recommend it to others.

KEC Site Plan and Elevations

KEC Exterior Wall Mock Up

At the start of a project it is very important to construct an exterior wall mock up.  The mock up is used for several purposes including material selections, constructability, and performance.  This project team used the mock up for final exterior material selections and to review constructability details.

We first started by placing the concrete slab.  This allowed us a trial run on the concrete mix design and resulted in some modifications to the mix design to allow the concrete to be more workable during the placement.  

[mock up slab pour]

Next we framed the walls and roof with 2x wood framing and plywood sheathing.  The building will be framed with FSC certified lumber.  Then (2) layers of 15# felt paper were installed as the buildings vapor barrier.  This is important to keep moisture out of the building.

[mock up wall framing and sheathing]

Next the stone veneer was installed.  The stone is a locally sourced fieldstone found in close proximity to the project site. 

[mock up stone veneer and cavity wall]

We sampled different mortar colors and joint types on the mock up so that the preferred color and joint method could be selected.  On the bottom wall section we used a recessed joint and the top section is a flush joint.  Because the stone has an irregular surface, the flush joint tends to look very wide.  The team preferred the recessed joint on the bottom half of the wall.  While installing the stone, the precast concrete sill was not yet available so we had to put in a piece of pink styrofoam to allow us to complete the stonework.  Then when the precast concrete sill was fabricated, we were able to slide it right in without holding up the schedule.

[mock-up stone veneer]

A sample window was installed.  The window is a Marvin aluminum clad wood window and the wood is FSC certified.  Next a base course of Trex was installed at the watertable at the very bottom of the wall.  Trex is very durable and corrosive resistant, does not need to be painted, and is made from 100% recycled material so it is a good choice for this application.  Then the cedar trim was installed which will also be FSC certified.  The roof is a painted aluminum standing seam metal roof with matching snow rails.  The siding on this project is a cement board product, which is an alternative to wood siding.  This is a good sustainable option because it is extremely durable, it outlasts wood, it holds paint very well, and it is also very fire resistant.  We sampled two different colors and manufacturers and the team preferred the top half which is Hardie Plank Countrylane Red.  The final step was to stain the cedar trim using a low VOC stain from Benjamin Moore.

[completed mock-up]

In addition to material selections, the team learned a great deal from the mock up.  We were able to work out some dimensional details on the stone veneer.  The concrete mix design was modified to allow a more workable mix.  Most important were the details on the cement board siding and wood trim.  This is not a standard everyday design because of the large exposure ship lap detailing.  The carpenter foreman had to set up custom jigs and experiment with the blocking and shimming and corner details until he was able to find a good compromise that met the design intent and would be a durable long lasting detail.  Again this is a very important exercise because it allows the team to work out many of the details on a small scale sample of the building that may not be evident on paper.  It provides a hands on opportunity for the trades performing the work to get familiar with the installation and raise any concerns to the team before working on the actual building.  This will ensure a better quality product and will avoid the potential for added costs and schedule impact down the road.

KEC Week 9

I have a little catching up to do on this project since the idea to blog about it came to me several weeks into construction.  I will take this time to bring you up to speed with general progress to date.  There is a long and interesting story of the Preconstruction phase that I will get into at another time.  I will also focus many future entries on the sustainable features of this project.

Quick project stats: 31,818sf.  LEED Platinum goal.  Energy Net Zero goal.  Cost not disclosed at client request.  Schedule 15 months (Spring '11 to Summer '12).  Project website with webcam access: http://www.choate.edu/aboutchoate/kohler_environmental_center.aspx

[site prior to start of construction]

We mobilized in late March, starting first with our site erosion control in accordance with the Erosion and Sedimentation Control Plan (ESC) and Storm Water Polution Prevention Plan (SWPPP).  The project was kicked off with a groundbreaking ceremony on April 1, 2011.  Everyone was in good spirits despite the raw weather and snow flurries.

[groundbreaking]

Once the ceremony was complete we continued with erosion control and a small but necessary amount of tree clearing to allow for a new entry drive to access the new building.  Erosion control for this project originally consisted of silt fence and temporary sedimentation traps (TST), along with track pads consisting of crushed stone at the site entries.  LEED requires an ESC plan under one of its prerequisites (SS P1) and the intent is to reduce pollution from construction activities by controlling soil erosion, waterway sedimentation and airborne dust generation.

[silt fence to protect adjacent property from run-off]

[silt fence and hay bales to protect adjacent property from run-off]

[temporary sedimentation trap TST with silt fence and topsoil stockpile]

[silt sock in adjacent catch basin to prevent silt from entry to stormwater system]

[TST]

Topsoil was stripped and stockpiled on site.  Because this site was previously used as a farm years ago, the topsoil depths ranged from 18"-20" which is an unbelievable amount compared to what we would typically see on most sites.  The topsoil stockpile was protected by surrounding it with silt fence and spraying it with grass seed to establish root development and prevent the stockpile from wind or water erosion.  When the project is complete the topsoil will be re-spread to similar depths on site and reseeded with native hay seed to restore the site to its natural state.  This depth of topsoil also helps to establish the native species without the need for a permanent irrigation system.

[topsoil stockpile with silt fence and grass seed to prevent airborne dust and erosion] 

April and May were particularly rainy this year.  These heavy rains coupled with our specific soil conditions, which consists of a very fine clay, presented some challenges with respect to stormwater management.  The SWPPP was modified to include haybales, check damns, detention basins, and the use of a product called Floc Logs.  This was a really very interesting product that we had not used before.  The very fine silts from the red clay on site remained suspended in the stormwater and did not settle out at all resulting in a very high turbidity.  There was a general concern that this high turbidity water could have adverse affects if it left the site and entered nearby streams without first being treated in some way.  Also because of the tight clays and frequency of rains, the TST's were at maximum capacity and took a long time to drain down if at all.  We set up what was best described as a chute, similar to a water slide with jute mesh and Floc Logs.  Stormwater was then pumped down the chute and as the turbid water passed over the Floc Logs, the Floc Logs act to bind the fine silts together so that they settle out of the water and drop to the jute mesh on the bottom of the chute.  The water comes out the low end of the chute crystal clear.  You really need to see it to believe it, but it worked great and helped to alleviate our stormwater management challenges.

[TST with hay bale check dams]

[stormwater detention]

[modified stormwater detention area with pipe chute (center coming straight at the camera) with jute mesh and Flog Log feeding into detention area]

[sample Flog Log photo, Floc Logs are the blue sqaures on the right and are about 18" x 6" and they are like a large cube of Jello]

Our building excavations started on the East wing which is a 2 story structure with a basement.  Prior to construction, a geotechnical engineer uses a drill rig to drill or bore down into the ground to determine what type of soil conditions are present on site.  They may encounter a wide range of materials like gravel, clay, glacial till, or bedrock to name a few.  This information is used by many of the team members to design foundations and plan for site excavations.

[sample drill rig]

The original soil boring logs indicated that we would encounter weathered bedrock while excavating for the basement when we went about 10 feet below grade and these borings proved to be very representative of the actual conditions.  The main excavation was down 14' and the deepest point for the elevator pit and sewerage ejector pit were down about 18', which means we had between 4' and 8' of rock to remove.  Our hopes were that the weathered bedrock would peel up with the excavator and as we got into harder bedrock it would need to be broken up using a hoe ram.  These methods were used and found to be effective.

[excavation for basement foundation]

[bedrock removal]

[bedrock removal (red) and crushed stone (blue) base material for foundations]

This gets us pretty well caught up.  We have just started basement foundations.  We start with formwork and rebar for the basement footings and walls.  We are working the foundation crew long days to make up some of the time lost due to the rains this spring.  We expect to be able to make back the lost time with a combination of crew sizes and overtime over the course of the summer.

[basement foundation footing formwork on crushed stone]