<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi there!<div class=""><br class=""></div><div class="">Your question is one I have wondered about myself in similar, although specifically different situations. Basically the idea of how to change an existing non conditioned attic space into a conditioned attic and the possible repercussions. </div><div class=""><br class=""></div><div class="">Can you please explain this approach further: "My approach would be to create ventilation above the insulation to allow vapor to continue to</div>vent to the highest point."<div class=""><br class=""></div><div class="">Thanks,</div><div class="">Lisa</div><div class=""><br class=""><div apple-content-edited="true" class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Lisa Rigazio AIA </div><span class="">rigazio designs, llc | <a href="http://www.rigaziodesigns.com" class="">www.rigaziodesigns.com</a><br class=""></span><div class="">240-350-0532 | <a href="mailto:lisa@rigaziodesigns.com" class="">lisa@rigaziodesigns.com</a></div><div class=""><br class=""></div><div class=""><br class=""></div></div><br class="Apple-interchange-newline"></div><br class="Apple-interchange-newline"><br class="Apple-interchange-newline">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Oct 28, 2015, at 7:52 PM, <a href="mailto:conservationarchitect@rockbridge.net" class="">conservationarchitect@rockbridge.net</a> wrote:</div><br class="Apple-interchange-newline"><div class="">I have a client that has renovated a 1940's house by gutting the plaster and<br class="">installed close cell foam and fiberglass (flash and batt) against the<br class="">siding. This is not what my choice would have been, but I was not involved<br class="">in that decision. However, I expect that part of the thermal envelope to be<br class="">tight. They are now living there. They had the floor above the<br class="">basement-crawlspace and the ceiling above the second floor insulated with<br class="">fiberglass. The ducts and air handling units are in the attic. The roof is<br class="">metal with hips and roofing boards with gaps. Since I expect the ceiling<br class="">with duct penetrations and fiberglass to be leaky, I am recommending foaming<br class="">the rafter spaces to bring the attic into the conditioned thermal envelope.<br class="">This will capture the likely heat losses (winter) from leaky ceiling and<br class="">ductwork. However, I was told by an insulation contractor that leaving the<br class="">old fiberglass could create humidity problem. He did not know why.<br class="">However, he had that experience. I wonder if his experience was closed cell<br class="">foam that trapped the house humidity, therefore raising the dew point.<br class="">Without expressly heating the attic, it could drop below the higher dew<br class="">point from elevated humidity. However, if we use a vapor permeable foam<br class="">such as open cell foam, the vapor would not be trapped. My approach would<br class="">be to create ventilation above the insulation to allow vapor to continue to<br class="">vent to the highest point. I expect that incidental leakage for the ducts<br class="">and the ceiling insulated with common practice fiberglass, would deliver<br class="">heat. However, expressly providing conditioned air supply and return would<br class="">provide assurance of avoiding a problem. They did a pretty good job<br class="">installing the insulation for that kind of system. Since we do not need to<br class="">heat the attic to comfort, could that be an intermediate zone that helps<br class="">insulate the main living areas by leaving the ceiling insulation. Or is<br class="">there a reason that we must remove the newly installed fiberglass batts in<br class="">the attic floor.<br class=""><br class="">Hope you all are still out there.<br class=""><br class="">Eli <br class=""><br class="">_______________________________________________<br class="">Greenbuilding mailing list<br class="">to Send a Message to the list, use the email address<br class=""><a href="mailto:Greenbuilding@bioenergylists.org" class="">Greenbuilding@bioenergylists.org</a><br class=""><br class="">to UNSUBSCRIBE or Change your List Settings use the web page<br class="">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org<br class=""></div></blockquote></div><br class=""></div></body></html>