From: 	Mark Woglom <markw@opechee.com>
To:	AQJ@portlandmaine.gov
CC:	JF@portlandmaine.gov; DGA@portlandmaine.gov; BAB@portlandmaine.gov
Date: 	8/7/2012 2:34 PM
Subject: 	RE: Glass Specs
Attachments:	OPCH-3062.jpg; OPCH-3085.jpg

Thanks Alex,

Essentially, the more visible light transmission, the worse the energy rating.  Here is a great website that shows you the glass options available with different standards:

http://glassconfigurator.ppg.com/default.aspx

[cid:735075517@07082012‑1FA3]

As you'll see, it you select glass options with a VLT of greater than 60%, your options for low SHG coefficient get real low.  There is a product called Starphire glass that combines clear glass with low SHG coefficients, but it is wildly expensive ... often used in aquariums .... or "money is no object" type of retail environments.

As a reference, the Hampton Inn has a VLT of .70, and a SHG coefficient of .45.  The SHG coefficient of .45 isn't "too" bad, but for a LEED project, we would have needed something better, which would really preclude our getting to a VLT of .70 or above.

In downtown Concord, NH we just designed, and built, a 92,000 sq. ft. office building.  That building was LEED certified, and used clear glass.  The glass had a VLT of .64, and a SHG coefficient of .32.  I think that project looks fine.  If I had my choice, I'd use that same glass at this project, with the exception of the preference for a blue tint on the office curtainwall, trading visibility for architectural interest.

In my opinion, the VLT tech standard of .7 is overly ambitious in terms of visibility through the glass, and comes at a significant detriment to energy efficiency.

Hope this helps.

Mark Woglom
President

[cid:735075517@07082012‑1FAA]

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

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

________________________________
From: Alex Jaegerman [mailto:AQJ@portlandmaine.gov]
Sent: Tuesday, August 07, 2012 1:51 PM
To: Mark Woglom
Cc: Barbara Barhydt; Deb Andrews; Jean Fraser
Subject: Re: Glass Specs

Hi Mark.
Congratulations on getting your TIF last night.

Thanks for the information on the glass parameters.  I will study your request about the fenestration and glass cladding.  We are always interested in improving our understanding of the building products, energy efficiency, and the implications of our requirements.  The Low E glass at .69 seems at first glance like a reasonable approach.  We will look at the material you sent and get back to you with further response.

Alex.

>>> Mark Woglom <markw@opechee.com> 8/7/2012 1:33 PM >>>
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:735075517@07082012‑1FB1]

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

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