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Ready for Drywall

5/31/2014

We had torrential rain yesterday so we couldn't get the drywall delivered. To stay on schedule the good folks at Allsouth made a Saturday delivery for us this morning.

It's really cool how they 'boomed' it in through the patio door by the kitchen. Getting all that rock into the house would have been a back-breaking job if they had to manually haul it up to the main level.

We're on track for the sheetrock crew to start on Monday. Thanks Allsouth!!

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Rain Day

5/31/2014

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We had some pretty heavy rain on Friday. It will sure be nice when we get the downspouts installed next week. The downspouts will feed into corrugated plastic tubing that we buried before backfill, so the water will all be diverted around and away from the house.

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Power to the House

5/31/2014

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We passed the insulation inspection on Wednesday. Amicalola Electric arrived promptly on Thursday morning to pull the electric service from the transformer to the house. WooHoo!! we finally have electric in the house.

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Air Infiltration - Blower Door Test

5/31/2014

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A blower door is basically an industrial fan mounted in a frame that fits into an exterior doorway. The fan pulls air out of the house which lowers the pressure inside. The higher outside air pressure causes air to flow into the house through all unsealed cracks and openings.

The blower door unit has pressure gauges to calibrate the pressure difference being used for the test and a manometer that measures the total amount of air flowing in through cracks and openings.

Air infiltration is measured in cubic feet per minute (CFM) and is then calculated as a number of Air Changes per Hour (ACH)

Georgia currently utilizes the 2009 IECC (International Energey Conservation Code) which mandates that all new homes must have an energy audit and must achieve an air infiltration rate of 7 ACH or less. As I wrote in a previous post (Air Infiltration - How Tight is Good Enough), this is a pretty poor standard and we are aiming to do much better. The 2012 IECC standard sets a much stricter standard of 3 ACH or less.

Normally, a blower door test is done after the house is entirely complete. We decided that we would do two tests: one with just the flash insulation and a final test when the house is complete. This allowed us to fill some leaks and make a few improvements before the drywall goes up. It also allows us to measure the effects of drywall and finishing on the overall performance.

Keith Jensen from Home Energy Shield did the test.

The total volume of the house (counting the basement) is about 45,000 cubic feet. Code allows 7 ACH which would be roughly 315,000 cubic feet per hour or 5247 CFM.

Our test came in at 2294 CFM, which is approximately 3.06 ACH.

We are very happy with this result. Tight construction, quality windows and flash-batt insulation have resulted in a package that just about meets the future IECC requirements and we don't even have the drywall installed yet.

Is it Cost Effective??
Based on the computer models, moving from ACH=7 to ACH=2 will save about 20M BTU of heating per year, which will save about $350 per year in electricity (neoTerra is all electric). This would be a savings of roughly $7000.00 over a 20 year period.

On the other hand, spray foam insulation is expensive. You have all the cost and labor of installing batts and even more expense and labor for the spray foam. You essentially insulate the house twice. The spray foam is labor intensive since all of the windows and floors have to be covered in plastic and taped to protect against overspray.

For neoTerra, the flash-batt system cost more than twice as much as just installing fiberglass batts. The fiberglass came to roughly $2.00 per square foot while the spray foam was more than $3.50 per square foot. At $7400.00 the cost of the spray-foam is sort of on the edge of being cost-effective if we only look at the savings on electricity.

As an additional consideration, however, reducing the heating load by 20M BTU/yera allowed us to save about $2000 on HVAC equipment.

My conclusion is that flash-batt insulation is cost-effective and will improve the comfort of the house.

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Flash Batt Insulation

5/29/2014

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Insulation is a big factor in any energy efficient design. As I wrote in a much earlier post, air infiltration would account for about 40% of our heat loss if we used conventional insulation so we looked at ways to build a tight envelope.

In the early design stage we looked at building with Structural Insulated Panels (SIPs). The SIP panels are typically made as a sandwhich that has OSB sheathing bonded to an insulating foam core. With SIPs you can construct very tight, energy efficient shells but the cost was just prohibitive.

We also investigated using spray foam to fill the wall and ceiling cavities but the foam is very expensive.

We decided to go with a "Flash-Batt" system. This technique uses a layer of spray foam against the outside walls to get an airtight seal and then conventional fiberglass batts, which are much less expensive, are used to fill the rest of the wall (or ceiling) cavity to get the desired R-value.

The spray-foam creates a vapor barrier against the oustide wall. The system has to be designed for the specific climate to avoid having moisture condense inside the walls, which would create mold or rot problems.

We used 1" of closed-cell foam in the walls (about R-7) along with R-19 Batts for a theoretical total of R-28. However, the 5 1/2" batts are being compressed into a 4 1/2" space so the actual R value is probably closer to R-24.

The ceilings have 2" of foam and R-25 batts for a total of R-39.

The basement walls are precast concrete panels from Superior Walls and have 2" of Dow blue board cast into the walls. Along with R-19 batts this provides a total R value of R-31.

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Painting Completed

5/26/2014

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The past couple of weeks have been really busy. The fiber-cement siding and soffits are all done and the exterior painting is complete except for the small roof over the front entry.

I decided to use clear Suntuf polycarbonate sheeting for the roof over the front porch. It is strong, lightweight and easy to install. http://www.palramamericas.com/Suntuf

It will keep the front entry sheltered from the rain but it still allows natural light into the foyer. We will cover the beam and fascia with fiber-cement and then paint it to match the rest of the trim.

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Design Patterns

5/12/2014

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I've been working on a post about Design Patterns and the various factors we thought about while we were designing the new house. I'm jumping the gun here, but Tracey is at the site and sent a few pics today that I just have to write about.

When we were initially going through the design we wanted to create public and private zones. Although the public area is merely a few feet from the private area we wanted the public area to feel expansive and dramatic while the private area should feel secluded and sheltered.

We utilized the change in terrain, a change in material and a step back to create the sense of two distinct outdoor environments.

The bedroom wing is positioned at the east end of the house where it is at grade and in the woods.

To define the public space we stepped the Great Room back to the north to create a two-story open outdoor area. The bedroom wing has no windows facing the public space and only looks out to the woods.

That's the theory... As the trees recover from construction and fill in, it's looking pretty good.

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Fiber Cement Complete

5/9/2014

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The siding is complete, the trees are green and the clouds have settled in on the mountain.

Life is good.

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Fiber-Cement Siding - Part II - Top Notch

5/9/2014

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Todd and his crew from Top Notch Siding has been making great progress on the fiber-cement soffits and siding. Everything is done except for a small area above the front porch, which they will finish on Friday.

The panels and trim are both fiber-cement but the Hardie battens are a different color than the Nichiha panels. It will be much more subtle after it's painted.

Note the lower batten that is in-line with the bottom of the metal siding. The siding on the kitchen cantilever is nicely aligned with the metal siding along the deck. This also happens to be the height of the railing that will be installed on the porch. A modern/minimalist design doesn't have any ornamentation (or gingerbread) to break up the structure so small details are a big factor in the overall appearance. Alignment and proportion are key elements in Modern design.

Kudos to Chuck, Tracey and all the craftsmen making the details come out right.

I'm getting kind of attached to that big red dumpster. Maybe we'll keep it as a permanent lawn ornament.

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Fiber-Cement Siding - Part I

5/6/2014

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We decided to use Fiber-Cement siding for about 50% of the house to provide a contrast to the ribbed galvalume.

Typical residential grade panels from Hardie or Nichiha are 5/16 inch thick, while the commercial grade panels are 7/16"

We are using the 5/16" residential panels rom Nichiha. It's a great product and its made in Georgia. In addition, NichiPanel is available in 12' widths, which reduces the number of seams and the potential for water leakage. Here's a link http://www.nichiha.com/home

The residential panels weigh about 2.2 lbs per square foot, so the larger panels can weigh 75 - 80 lbs. The panels go up quickly, but it takes a three man crew to support and fasten these heavy sheets.

We originally planned to use Tamlyn aluminum reveals between panels (see the How To section) but the logistics (and cost) of using the reveals was just too much.

We decided to use simple galvanized Z channel between panels and use thin battens to create shadow lines.

Here's a couple of pics. And... The trees are turning green!

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