From: 	Mark Woglom <markw@opechee.com>
To:	AQJ@portlandmaine.gov
Date: 	8/7/2012 1:36 PM
Subject: 	Glass Specs
Attachments:	Clear Glass.pdf; Low E Glass.pdf

Alex,

Give me a call when you have a minute.  I would like to discuss glass specifications in light of your technical standards, LEED, energy usage, and architecture.  The short version is the following:

1. You tech stds seem to indicate a Visible Light Transmission (VLT) of .70
2. The only glass that meets that standards is a a glass unit with clear glass on both panes (clear/clear), with no Low E solar coating on either pane.
3. Clear/clear glass has an abysmal energy efficiency rating, because it allows so much solar heat gain. SHG coefficient of .70.  There is no way I would build a building with that allows that much solar heat gain.  No only is it bad for energy efficiency, it is bad for occupant comfort.  Think "sun burn" if you are sitting next to a window.
4. If we use clear/low E, we can get to a .69 VLT (just shy of your .70 tech standard) but we substantially improve the SHG coefficient to .37.  This is what I would like to use everywhere but at the middle street office facade (glass curtainwall)  in the center of the building.  This will substantially improve our energy savings for LEED, and for our green building energy standard required for the TIF.
4. We would like to have some interest in the glass architecture for glass curtainwall.  I am not looking for reflective, but I would like to use blue tinted glass on the outer pane, and Low E on the inner pane.  That will drop our VLT in that area to .44.  I understand the goal of the tech standards (visible activity), and I think I can overcome the decreased interior visibility with a brightly lit lobby behind the curtainwall.  In my opinion, using clear glass on that curtainwall would significantly detract from the architecture.

Let's discuss after you've had a chance to review.

Mark Woglom
President

[cid:336161417@07082012‑1F8E]

Opechee Construction Corporation
11 Corporate Drive
Belmont, NH 03220
P (603) 527‑9090
C (603) 387‑7172

markw@opechee.com<mailto:markw@opechee.com>