<div dir="ltr">I've just been reading a bunch about this general subject, in documents suggested by folks here on this list, and the conclusion I came to was that above R30 (I think that was the figure), and with careful attention to air sealing, ventilation can safely be omitted. Now in my case I'm separating the rafters supporting the roof sheathing (2x6) from the 2x4 purlins to which the sheet rock is going to be attached, creating a thermal break that your design only approximates, but someone here can surely speak to how much those I joists conduct heat and the degree to which that impacts your overall R-value.<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Jan 21, 2017 at 10:02 AM, Clarke Olsen <span dir="ltr"><<a href="mailto:colsen@fairpoint.net" target="_blank">colsen@fairpoint.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">I am building a 750 sqft building with two single plane (shed) roofs, using 12" I joists @ 3/12 pitch. <div>Can we just stuff that 12" with Roxul, or is ventilation needed?<span class="HOEnZb"><font color="#888888"><br><div>
<span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word"><span class="m_1772556186815151180Apple-style-span" style="border-collapse:separate;color:rgb(0,0,0);font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word">Clarke Olsen<br><a href="http://clarkeolsendesign.com" target="_blank">clarkeolsendesign.com</a><br>373 route 203<br>Spencertown, NY 12165 <br>USA<br><a href="tel:(518)%20392-4640" value="+15183924640" target="_blank">518-392-4640</a><br><a href="mailto:colsen@taconic.net" target="_blank">colsen@taconic.net</a><br><br><br><br></div></span></div></span></div></span></div></span></div></span></div></span></div></span></span>
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