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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I said ‘usually’ requires. Building is about understanding how materials work and how they work together. Concrete expands and contracts – the ground or structure underneath it expands and contracts. It is like two people dancing to different songs. This is why we put control joints in slabs (to relieve stress and create predictable cracking). This is also why we separate materials (a layer of sand between the ground and the concrete to allow for movement) or we increase the strength of a material to resist cracking (eg. Reinforcement in concrete or increasing the thickness of a material)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I read in a later post that this slab you don’t like is only two inches and supported by wood framing. You also said that it is thicker than the designer wanted? This is an atypical floor so it raises lots of questions. Is the framed floor strong and stiff enough to support a 2” slab (if it is thicker than the designer wanted then they were probably specifying a gypsum floor with something over it). Is the slab designed to resist movement (sufficient reinforcement and control joints)?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I have the feeling that this was a conventionally framed floor and the concept of adding mass as a finished concrete slab floor was an afterthought and not well thought out. If the floor is not designed to hold the weight of 2” concrete it will fail in some way or compromise the structure – it will definitely continue to cause the concrete to crack. Anything you put over the concrete will show the cracks through it or form new cracks. Removing and replacing the concrete is not really a solution. 2” concrete has to be reinforced substantially and control joints cut in a tight grid pattern and still there will be odd cracks. Going thinner means you are basically pouring concrete tiles and even a 2’ grid pattern will crack over a framed floor.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The only reliable way of achieving mass of consistent density would be tile on a thickset (tile on 1-1/2” of mortar) and that is tricky. Tile on a couple of layers of cement board is a possible option if the tile is fully bedded (no air gaps)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> Greenbuilding [mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>KTOT (g)<br><b>Sent:</b> May-13-13 10:20 AM<br><b>To:</b> 'Green Building'; topher@greenfret.com<br><b>Subject:</b> Re: [Greenbuilding] Passive solar home--concrete overlay re thermalmass<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>I am not clear on what you are saying. Are you saying simply applying overlay material (as was originally used in a bathroom, which is not thermal mass so was not an issue re overlay vs. bare concrete) will not work, that something else is required? Or a layer between the concrete and the overlay?<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Also my understanding is density isn’t the issue specifically re thermal mass, rather is an issue of earth materials (stone, water, clay, etc.) vs. non-earth materials.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Re the slab, it appears the cement was left sitting in the truck multiple hours with no retardant added and a very excessive amount of water was added, curing/finishing was likely improper, and possibly more. I probably didn’t mention the very severe cracking throughout the floor in my original post. People also have different opinions on whether one can just cover a defective slab or if cracking will cause problems in the future as well. Some of those issues are still be sorted out. Meantime, I’m focusing on the thermal mass aspect of overlay atop a slab.<o:p></o:p></span></p></div><div><div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <o:p></o:p></span></p></div><div><div><p class=MsoNormal style='background:whitesmoke'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <a href="mailto:terrain@shaw.ca" title="terrain@shaw.ca">John Salmen</a> <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:whitesmoke'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Sent:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Monday, May 13, 2013 10:58 AM<o:p></o:p></span></p></div><div><p class=MsoNormal style='background:whitesmoke'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>To:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <a href="mailto:greenbuilding@lists.bioenergylists.org" title="greenbuilding@lists.bioenergylists.org">'Green Building'</a> ; <a href="mailto:topher@greenfret.com" title="topher@greenfret.com">topher@greenfret.com</a> <o:p></o:p></span></p></div><div><p class=MsoNormal style='background:whitesmoke'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Subject:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Re: [Greenbuilding] Passive solar home--concrete overlay re thermalmass<o:p></o:p></span></p></div></div></div><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p></div></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The bonding of a tile or dissimilar material to a concrete slab usually requires a separation or slip sheet of some sort as well as a trowel pattern that will create air pockets. This is different that simply a concrete resurfacing material. Resurfacing is typically a very finely graded cement product with modifiers to allow for bonding and movement. The density of these materials would be typically high possibly exceeding the concrete slab. I can’t see an issue that would involve removing a slab unless it is totally f_____ for other reasons.<o:p></o:p></span></p><p class=MsoNormal> <span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> Greenbuilding [<a href="mailto:greenbuilding-bounces@lists.bioenergylists.org">mailto:greenbuilding-bounces@lists.bioenergylists.org</a>] <b>On Behalf Of </b>Vadurro, Rob, EMNRD<br><b>Sent:</b> May-13-13 8:07 AM<br><b>To:</b> <a href="mailto:topher@greenfret.com">topher@greenfret.com</a>; Green Building<br><b>Subject:</b> Re: [Greenbuilding] Passive solar home--concrete overlay re thermal mass<o:p></o:p></span></p></div></div><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I believe the concern is the transfer of heat between different materials. I can’t remember where I saw it, but there was a table showing the transferring heat between base and finish materials, say tile to concrete slab below in passive solar conditions and the rate of transfer was much less than one might think. The joint between the two impeded the heat transfer, in other words. I would think an acrylic additive may impede the transfer even more. The best is always to not cover the slab, only color it, if heat retention in the slab is the goal.<o:p></o:p></span></p><p class=MsoNormal> <span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><div><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Rob Vadurro, AIA<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Park Architect<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>New Mexico State Parks<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>1220 South Saint Francis Drive<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Santa Fe, NM 87505<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>505-476-3383<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>505-476-3361 fax</span><span lang=EN-US style='font-family:"Baskerville Old Face","serif";color:#1F497D'><o:p></o:p></span></p></div><p class=MsoNormal> <span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> Greenbuilding [<a href="mailto:greenbuilding-bounces@lists.bioenergylists.org">mailto:greenbuilding-bounces@lists.bioenergylists.org</a>] <b>On Behalf Of </b>Topher<br><b>Sent:</b> Monday, May 13, 2013 8:39 AM<br><b>To:</b> Green Building<br><b>Subject:</b> Re: [Greenbuilding] Passive solar home--concrete overlay re thermal mass<o:p></o:p></span></p></div></div><p class=MsoNormal> <span lang=EN-US><o:p></o:p></span></p><div><p class=MsoNormal><span lang=EN-US>On 5/13/2013 1:07 AM, KTOT (g) wrote:<o:p></o:p></span></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal><span lang=EN-US>Does anyone have experience or knowledge about this? Using or not using a concrete overlay product for the top layer of a floor for thermal mass, vs. a plain darkly stained concrete slab <o:p></o:p></span></p></blockquote><p class=MsoNormal style='margin-bottom:12.0pt'><span lang=EN-US><br>A concrete overlay product is likely to be roughly similar in thermal characteristics to a concrete slab. Meaning that you will just have a thicker thermal mass. It seems unlikely that you should be worried about <i>too much</i> thermal mass in a passive solar house. The overlay product might have a lower specific heat, or conductivity, wither of which will reduce it's effectiveness somewhat. Remember to stick with a dark color.<br><br>Thank You Kindly,<br><br>Corwyn<o:p></o:p></span></p><pre><span lang=EN-US>-- <o:p></o:p></span></pre><pre><span lang=EN-US>Topher Belknap<o:p></o:p></span></pre><pre><span lang=EN-US>Green Fret Consulting<o:p></o:p></span></pre><pre><span lang=EN-US>Kermit didn't know the half of it...<o:p></o:p></span></pre><pre><span lang=EN-US><a href="http://www.GreenFret.com/">http://www.GreenFret.com/</a><o:p></o:p></span></pre><pre><span lang=EN-US><a href="mailto:topher@greenfret.com">topher@greenfret.com</a><o:p></o:p></span></pre><div class=MsoNormal align=center style='text-align:center'><span style='font-family:"Calibri","sans-serif"'><hr size=2 width="100%" align=center></span></div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>_______________________________________________<br>Greenbuilding mailing list<br>to Send a Message to the list, use the email address<br><a href="mailto:Greenbuilding@bioenergylists.org">Greenbuilding@bioenergylists.org</a><br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a><o:p></o:p></span></p></div></div></div></div></body></html>