Posted By: PaulTHowever Cellulose materials are not High thermal mass - they are medium thermal mass. THis means that you have a medium amount of thermal mass available with a medium amount of thermal resistance. This means that the wall can asborb a relatively significant amount of heat at a slow rate. The home will quite repsonsive to heating and have slow release quantity of thermal mass.

That's how I see it too. And I'd say that's what makes it work well for us in the Irish climate - we need a reasonably responsive house to heating because the weather changes so often but also need a bit of slow release to even out the temperature swings. It seems to work from where I'm sitting! As I said above - if you want figures on real buildings in the UK I'd get in touch with Neil May at NBT.

(@Viking House: Hi Seamus: yes it's me - glad to hear you're building some houses this way. Will send some photos sometime).

Actual Peter I do not agree that we need to go heavyweight

The important point, lost in a long post, is that Reducing heat loss/gain is the most important factor!

The majority of heat gain is through windows. with actualy very little (relatively, in the UK) coming in through roofs.

The most effective reduction in heat gain in a roof is to use a breathable foil layer under the tiles.

Also please do not confuce temperature stability with reduced heat loss. For "thermal mass" to buffer temperatures you need to put extra heat into the building on every heating cycle. Far better to focus on reducing heat loss.

Hi dickster

Have you thought about using recycled concrete blocks with a wet plaster on your internal walls?

- especially on walls opposite south facing windows where they can capture solar gain (The most important benefit of "thermal mass" in my view).

Hi Paul,

Posted By: PaulTThe important point, lost in a long post, is that Reducing heat loss/gain is the most important factor!

Of course, that is what insulation is for.

Posted By: PaulTThe majority of heat gain is through windows. with actualy very little (relatively, in the UK) coming in through roofs.

I find this impossible to believe. I have two rooms with identical windows, same elevation, one is a room in the roof, one on the storey below. The room in roof becomes impossibly hot during a summer day, the one below much less so. Sometimes the difference is 10 degrees.

Posted By: PaulTThe most effective reduction in heat gain in a roof is to use a breathable foil layer under the tiles.

Yes foils are interesting, especially for room in roof where there is often a lack of height. Are you aware of any data from trials supporting this position - that foil is most effective?

Posted By: PaulTAlso please do not confuce temperature stability with reduced heat loss. For "thermal mass" to buffer temperatures you need to put extra heat into the building on every heating cycle. Far better to focus on reducing heat loss.

Have I been confusing these two? sorry if I have. I am responding really to the two graphs Viking House referred to on his website.

‘dense insulation kept the house 4 degrees warmer.’

And something similar for keeping cool in summer?

Are you are suggesting that the house with denser insulation, that is cooler in summer and warmer in winter, will use more fuel for heating and cooling overall?
In which case, I will have to think some more, very interesting tho, thanks again.

Peter

Posted By: PaulTHowever in a long heat wave it is quite posssible for this thermal mass to stay warmer for longer.

No doubt about that. I used to live in a small stone cottage in Glossop. In the hot summer of 1990 the internal temperatures made it into the 30s centigrade and no amount of open windows made any difference as there was so much heat absorbed into the two foot thick stone walls. I believe that high thermal mass is useful in climates that high large diurnal temperature swings (Colorado and such like are places that come to mind) but in a damp climate like the UK where there isn't much diurnal range, or a climate like mine where the temperature may not dip below 24C overnight, it's actually a hindrance rather than a benefit. The further north one is located, the less usable solar gains are anyway and triple glazing reduces these modest gains even further.

As PaulT points out, it's the temperature of internal surfaces that is very important for comfort. As a case in point, my home office is at the NorthEast corner of the house and previously had no insulation in the walls at all (12" brick + 8" stone on the North wall and 8" brick on the east wall). Even though I could maintain the air temperature at 21.6C, it didn't feel comfortable as the wall surface temperatures were around 14C with an outside temperature of -11C (as revealed during an energy audit with an IR thermometer). This past year, I insulated internally with just 12.5mm of foil-faced polyisocyanurate board (and took great care with airtightness details). Now this year with even colder temperatures outside, the internal surfaces are much warmer (I haven't had the chance to measure but I'd estimate that they're between 19 and 20C) and, with the same internal air temperature, I feel much warmer as there isn't a cold radiator surrounding me. By the way, that tiny amount of insulation effectively doubles the R-value of the wall.

Paul in Montreal.

Posted By: djh

I am responding really to the two graphs Viking House referred to on his website. ‘dense insulation kept the house 4 degrees warmer.’

I don't see this on the page that was linked to and Google can't find it on the site or indeed anywhere on the web. Where did you find this quote, please?

Hi djh,

its in this thread, in the previous page, first post by Viking House, not in his link

'Check out how cold it got outside (10 degrees), in the Fibreglass house the temp dropped to 14 degrees and in the Cellulose house the temp dropped to 18 degrees. So the dense insulation kept the house 4 degrees warmer.'

Sorry for any confusion,

Peter

Posted By: Peter ClarkHave I been confusing these two? sorry if I have. I am responding really to the two graphs Viking House referred to on his website.

‘dense insulation kept the house 4 degrees warmer.’

And something similar for keeping cool in summer?

Are you are suggesting that the house with denser insulation, that is cooler in summer and warmer in winter, will use more fuel for heating and cooling overall?

and

its in this thread, in the previous page, first post by Viking House, not in his link

'Check out how cold it got outside (10 degrees), in the Fibreglass house the temp dropped to 14 degrees and in the Cellulose house the temp dropped to 18 degrees. So the dense insulation kept the house 4 degrees warmer.'

I don't follow your logic here Peter. What Viking House said about the house staying 4 degrees warmer refers to the graphs on his web page and that is discussing a hot SUMMER performance. I don't think I've seen any implication by anybody but you that the house with denser insulation will stay warmer in the winter!?

Actually, I do agree that exploiting decrement delay in winter will increase the coldest internal temperature but it will also reduce the hottest internal temperature and I believe that the same amount of fuel will be required overall. This effect can be equally well obtained by the use of thermal mass inside any insulation.

Hi djh

I actually believe that house B will use less fuel to heat the house than house A which was one of the reasons for putting up the webpage. Many of my Polish builders believe this instinctivly and have seen it in practice. If they are building a house for a client the heating cost for the house is reduced dramatically when they choose to Externally Insulate with Dense Paroc Rockwool Insulation over Polysterene. The U-value of the wall doesn't change just the density of the insulation. If it is really Cold outside you will choose your heaviest coat which would have the same U-value (thickness) as your lighter coat if tested.

When they started studying heat loss with 3D Thermal Imaging cameras in Sweden they discovered that heavy insulation worked better and that heat moving in cylindrical patterns through dense insulation cannot be detected by a hotbox test.
So the U-value calculations we are using are not accurate!

I've tried quoting some people here but I can't make it work, am I doing something wrong?

VH - I would, of course, use insulating block work to reduce thermal bridging on internal walls? (this is a green building forum)

As "internal" ground temperatures are stable and relatively high then the amount of thermal resistance required is actual low.

- This is the method advised by Passiv Haus
----------
The sense of touch - hot an cold - is not as dependent on temperature as you might think. What we are actualy sensing is a rate of temperature change in our nerve cells. So two materials witht he same temperature can fee very different. So it is quite possible for a 'warm' wall (say 20) to feel cold compared to a cold piece of insulation. This is one of the reasons why the actual surface material is the most important layer of all.

- Wood cladding is possibly the best surface material you can chose:
It has a low conductivity (warm sup quickly)
It has a lower emissivity than most surfaces (0.75), reflecting more heat back.
--------------------------
Thermal comfort theory - In a typical indoor environment with low air movement (<.1m/s) and moderate humidity (say 50%) then our sense of thermal comfort is defined as being approximately 50/50 balance of air temperature (dry resultant) and mean radiant temperature.

The mean radiant temperature is dependent on the emissivities and surfae temperatures across a room.

So it is a fact that if surface temperatures are raised by 1C then the air temperature can be lowered by 1C to achive the same level of thermal comfort.
(It is for this reason that I recommend secondary radiant heaters in bathrooms.)

--------------------------

<blockquote><cite>Posted By: Viking House</cite>Hi djh

I actually believe that house B will use less fuel to heat the house than house A which was one of the reasons for putting up the webpage.
</blockquote>

I think that you will find that belief is not enough on this forum.

(VH - please accept that I am not putting up needlessly critical posts, but it is the case that there is a huge amount of greenwash and misleading advertising out there and this forum is a place to get critical analysis).

Providing information on temperature variations is not enough to establish lower heating input. (Unless I have missed something on web site and postings?)
- I have taught this theory at post graduate level and run simulations on the same building with different thermal mass interiors and have found no evidence to support your theories.
- The only basis I can think of is a reduction intemperature gradients because of the buffering effect on the internal heat capacity, but as I have said before the heat loss through walls and roofs is only a tiny fraction of the total in well insulated homes

Don't worry!
The important thing is that you are here and engaging with various people interested in green building ranging from University lecturers, Architects, Acusticians, Structural Enginerrs, builders, window makers and many other walks of life.
You will get honest and open opinions.
The key thing to remember is that all building is a compromise and that were the line is in the sand...
(eg I would not touch Polyurethane with a barge pole but am happy to use EPS, others will only use 'natural' materials)

Hi Paul

I would appreciate your comments on PU in the Renovation section.
Who is the Acoustics guy? He might be able to explain this! I built 2 sound studios for two friends, they are both insulated to similar thickness's with Rockwool and are of similar size. The quieter and warmer one is insulated with 200mm of 100kg density Rockwool and the other is insulated with 200mm of 50kg density Rockwool. The second one needs a heater and the first one doesn't. They both have similar equipment and similar usage.
They explained it to me by saying that the sound is converted into heat going through the insulation or something but it went over my head!

Having problems signing in, but can just about get postings up...

I have seen this type of box used o produce some very dubious results...

Firstly the heat flow is downwards and can not be used to demonstrate performance in horizontal or vertical heat flows (because of convection currents)

The box is being used on cyclical heating basis and it would not suprise me if the time lag for the woodfibre was just over one hour.

The important factor is how much heat is being put into the upper chamber and what are the temperatures of these chambers - in reality I only care about the interior environment, air an surface temperaturesa dn not he exterior temperatures (as in this case)

Because of the heat loss from the rest of the box (other than the insualted 'floor') it is actaully impossible to draw conclusions... Heat loss is all about the weakest link.

Glass fibre is very open and it does have big issues with induced convection currents inthe insualtion layers (proven in Canada to increase effective u values in cold lofts by up to 100%)

One complicating factor may be the surface emissivity of the woodfibre(Reflecting heat back up), but of couse in a built environment this would not be exposed, the interior surface being paint, wood, lime render, etc)

- Using the type of box you describe I could even prove that Multi foil insulation "works"

I suspect that you would get the same results with a slab of concrete covered in Kitchen foil!

-------------------
It is an interesting fact that for most open cell insulation the higher the densisty the better the thermal resistance. This is because under a certain size air pockets lose the ability to have convection currents. So very dense mineral wool has a lower thermal conductivity.
This, of course, only goes so far so the best mineral wools have conductivities around 0.032 and trhe worst 0.044.
The layers of inuslation in dense mineral wool are also improtant - under Canadian building codes they must be laid perpendicular to the dierection of heat flow.
(I have noticed that this is not the case in straw bale building and they could be missing a trick!)

Acoustics - User name 'TIMBER'.
Regarding the energy in sound - this is tiny compared to typical heat energy - we are fooled because our ears are very sensitive to minute amounts of kinetic energy

I met a few Dutch professors at the PLEA conference in Dublin. I will as ask if they can root out the paper.

This (and the various links) really is important stuff - especially for those needing to upgrade walls in solid walled buildings (in UK) from the inside. But am I getting the right translation into practicalities - or even asking the right questions?

1. Heavy weight insulation probably not advantageous at same u value - but may have other qualities to recommend it (e.g. wood waste, allows movement of water vapour and evaporation)?
2. Still air a v. good insulator so lightish-weight products that hold air within their structure have real advantages and this is so even in thin layers (e.g. polystyrene)? But what about water vapour in our damp climate? Stick to sheeps wool or waste paper unless wall very dry or using MHRV? What about semi-permeable foams?
3. Surface treatment (e.g ceramic microspheres in paint) has real advantages too? What do the spheres do to movement of water vapour?