Timber Frame Pros Cons

[scottishjohn]

ok you gurus here is my simple view on this thermal mass thing 

we all use concrete slab and UFH -

-why?

cos its store heat and regulates how it releases it  and  most agree its the best way  ?

well you build a concrete house with insulation on the outside of the concrete  --you will have all the walls to act as a heat sink and storage device 

,which by its nature will stop rapid changes .

excess heat caused by solar gain I just do not see being a problem  if attention is paid to window area ,and suitable shading+ mvhr ,as we presume this house will be air tight whatever its built from   

what the house is built from should not make much of an impact on these  problems--that is a design problem not a fabric one

that to me sums it all up.

 

 shoot me down boys 

[SteamyTea]

31 minutes ago, JSHarris said:

milk went in first. 

Still the wrong way to make tea.

26 minutes ago, scottishjohn said:

we all use concrete slab and UFH -

-why?

Because plumbing is pretty unsophisticated and cannot, or will not, be designed properly.

You could have a solid timber floor and get similar characteristics, but the price is prohibitive.

[Jeremy Harris]

6 minutes ago, SteamyTea said:

Still the wrong way to make tea.

 

 

 

I agree!  I always just stick a tea bag in a mug and fill it from the boiling water tap, then add milk later.

[SteamyTea]

There is a saying that the milk should never, ever, touch the tea before the water.

Not sure how that is going to help decide between construction methods, but I find that tea helps the thought process no end.

[joe90]

1 hour ago, JSHarris said:

just stick a tea bag in a mug

 

NO, leaf tea in a pot, leave to “stew” then pour, (then add milk)

 

how far can we we get away from the OP without the mods interfering ?

[Bitpipe]

2 hours ago, JSHarris said:

 

Another thing to thank Newton for...

 

Reminds me of the argument I had years ago with my wife, over whether tea was hotter or cooler if the milk went in first.  I conducted an experiment (as you do) to prove it one way or the the other.  I ended up being right, tea does indeed end up hotter after a defined period of time if the milk goes in first.

 

The reason is that, because the milk near-instantly cools the incoming hot tea, the rate of heat loss from that point onwards is slower, so after a defined period of time that cup of tea ends up slightly warmer than the one where the tea went in first, heating the cup to a slightly higher temperature, and so increasing the initial rate of heat loss.

 

Now the wife and I both have degrees in electronic engineering, both physics and maths fans and, sadly, none of this has rubbed off on our children who are as addicted to snapchat as the rest of them.

 

However if I were to suggest a similar empirical experiment to settle an argument such as the one above, very quickly we would be moving to a separate investigation on how long it takes for a cup of tea to evaporate from a human sized form:)

 

BTW, I'm with you on units - when I did A Level physics many moons ago, the first thing we learned were SI units, and manipulation of unit nomenclature. Our physics teacher rightly pointed out that if you got stuck in a test and couldn't remember the exact formula, quite often you could figure out the bones of it by looking at the units provided and the units required for the answer.

 

Also, I noted this from helping the kids with their homework this week - 

 

Without units, science wouldn’t make sense. Units allow us to use numbers to describe the world. That’s why maths is called the language of science. Understanding units and using them correctly can make all the difference in the exams. You want to nail those maths-heavy questions in your GCSE Physics papers? Then you need to be at one with your units.

[SteamyTea]

34 minutes ago, Bitpipe said:

Now the wife and I both have degrees in electronic engineering

Thermal Inertia is really just how a capacitor charges and discharges.

So knowing that, where do you stand?

[Jeremy Harris]

3 hours ago, Bitpipe said:

Without units, science wouldn’t make sense. Units allow us to use numbers to describe the world. That’s why maths is called the language of science. Understanding units and using them correctly can make all the difference in the exams. You want to nail those maths-heavy questions in your GCSE Physics papers? Then you need to be at one with your units.

 

 This is right at the very heart of my issue with the term "thermal mass", the absence of any meaningful units to describe it.

 

It seems very clear that heat capacity (in any form, molar, volumetric or specific) is just not "thermal mass".  If those proponents of this term wish it to fit within an international accepted measurement system then they need to be clear as to what the term really means. 

 

If it means thermal inertia, as applied to the rate of change of temperature inside a building with respect to the rate of change of temperature outside the building, then that's fine, but it then needs to be defined in units that enable it to be measured.  This would then enable one building to be compared to another in a meaningful way, or enable those designing buildings to optimise those designs so as to achieve a target value for this aspect of a building's performance, by calculating the impact of particular material choices in the structure of the building.

[Bitpipe]

2 hours ago, SteamyTea said:

Thermal Inertia is really just how a capacitor charges and discharges.

So knowing that, where do you stand?

 

I leant to the s/w side of electronics, she is in h/w. It's a wonder we're still together.

[ProDave]

8 hours ago, nod said:

I frame and plaster quite a bit of TF Mostly student accommodation 

Its normal to have a 5 % retention 

The retention isn’t taken for TF 

We are paid to go back several times to sort out the cracks 

I have built 2 timber frame houses and neither had cracks in the plaster.

 

Indeed the present one, the first I have had with a vaulted roof hung from ridge beams, I almost expected some cracking where walls meet roof, but 3 years since plastering, not even the faintest hairline crack anywhere.

 

Is the problem on mass production sites that they are built and plastered too quick?  It was a year from our frame going up to it being plasterboarded, and another year before being skimmed.  Plenty of time for settlement?

[ProDave]

5 hours ago, JSHarris said:

 

Another thing to thank Newton for...

 

Reminds me of the argument I had years ago with my wife, over whether tea was hotter or cooler if the milk went in first.  I conducted an experiment (as you do) to prove it one way or the the other.  I ended up being right, tea does indeed end up hotter after a defined period of time if the milk goes in first.

 

The reason is that, because the milk near-instantly cools the incoming hot tea, the rate of heat loss from that point onwards is slower, so after a defined period of time that cup of tea ends up slightly warmer than the one where the tea went in first, heating the cup to a slightly higher temperature, and so increasing the initial rate of heat loss.

I had the same "discussion" but about white or black coffee.

 

One of the contributing factors was the black coffee was not only hotter, but closer to a black body radiator so would loose heat quicker than the cooler, lighter coloured white coffee.

[Bitpipe]

5 minutes ago, ProDave said:

I have built 2 timber frame houses and neither had cracks in the plaster.

 

Indeed the present one, the first I have had with a vaulted roof hung from ridge beams, I almost expected some cracking where walls meet roof, but 3 years since plastering, not even the faintest hairline crack anywhere.

 

Is the problem on mass production sites that they are built and plastered too quick?  It was a year from our frame going up to it being plasterboarded, and another year before being skimmed.  Plenty of time for settlement?

 

Ours was erected in November, peeing with rain. Got boarded in May and skimmed in June - no issues 3 years in.

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole

[ToughButterCup]

This is the sort of thread from which readers can  learn a great deal. 

That process  would be made easier without  ad hominem comments.  

[LA3222]

56 minutes ago, AnonymousBosch said:

This is the sort of thread from which readers can  learn a great deal. 

That process  would be made easier without  ad hominem comments.  

Not sure i would agree with this, I have skimmed each new comment on here and I see this as a white noise thread.

 

It is the age old argument which periodically pops up on this forum about thermal mass and never seems to reach a conclusion.  I would say a much more useful discussion would be around decrement delay as that seems to be a far more critical performance attribute to consider when building as opposed to whether thermal mass has relevance.

 

I daresay that the lay persons eyes reading this thread will soon glaze over - but that's just my opinion so feel free to continue this battle!!

[Gone West]

14 hours ago, ProDave said:

Is the problem on mass production sites that they are built and plastered too quick?  It was a year from our frame going up to it being plasterboarded, and another year before being skimmed.  Plenty of time for settlement?

+1 Ours was a few of years between the frame going up and boarding and skimming. No cracking. The same with fitting the windows. They said I should leave a gap at the top of the window to allow for settlement but I explained that the frame had been up for some time and they were happy.

[Patrick]

Back to topic :

Tea needs to be made putting loose leaves in a metal tea leaf filter. Adding hot water and let it stand for 4minutes. Adding milk at the end, not before taking the leaves out. ?☝️?

 

[ToughButterCup]

1 hour ago, LA3222 said:

Not sure i would agree with this, I have skimmed each new comment on here and I see this as a white noise thread.

[...]

 

None of us can know how much thought, research and further reading members do on their own initiative as a result of reading this thread.

It would be a pity therefore, if contributions were to lose their focus.

[Declan52]

19 minutes ago, Sensus said:

 

Yes, the analysis has to include thermal conductivity as well, but that's a separate factor, and I think needs to be kept separate, if only to remind people that you can have two thermal elements with the same U-value, but widely differing thermal mas (or thermal inertia... or whatever you choose to call it), and as a result they will perform differently in terms of transient thermal response.

 

Personally, I don't much care what we call it, so long as we all understand what effect it has, which for the most part I think we do.

 

I personally quite like ST's label of 'thermal inertia',  but whatever... I think we have to recognise that one or two random internet nerds aren't going to change what the rest of the industry calls it. We're stuck with 'thermal mass', whether we like it or not.

 

 

I actually don't think there's any disagreement about the theory. What it boils down to is that JS doesn't like the name. As above; I can live with that. I can even agree that it's not the best name that could have been chosen. But I'm practical enough to realise that all the bleating you like on a niche internet forum isn't going to change it.

 

One of my other interests is race car design and chassis set-up. Similar to JS, I used to get very uptight that a lot of people refer to dampers as 'shock absorbers', which is a similarly misleading and incorrect name. Then I realised that I was just being a bit of a tit - that it really didn't matter, so long as the people who needed to understand it knew what was meant when that term was used.

 

The rest of the world calls it thermal mass. Live with that.

 

On the other thread, JS makes the very clear statement that thermal mass does not exist as a parameter. IT DOES. It just doesn't have the name that JS would like it to have, because it uses the word 'mass' when - whilst relating to mass for its derivation - it isn't actually measured in units of mass.

 

He also stated that "Like all other supposed explanations for this mythical physical property, [someone else's practical definition of the term] fails because it doesn't define the units of measurement" and that " Thermal mass has no units, so how can anyone measure it, or define what is "high" or "low"?". He asked, me above - presumably expecting  me to be unable to answer - to state the units. I DID.

 

I also pointed him back at the very website he used himself to 'prove' his point, which also gives a definition for thermal mass that identifies its units... it's a definition you'll find, I'm sure, in any number of textbooks on the subject. Certainly (because I've just checked), I have it in my lecture notes from the Building Science lectures I took in the first year of my Architecture degree, three decades ago. This stuff is basic, and not at all new.

 

For someone who claims such great care for precision of nomenclature, I find it odd that he should be making these sorts of statements, or creating topics with titles like 'The Great Thermal Mass Myth".

 

Surely, by his own standards of accuracy, he should be renaming that topic "The Great Thermal Mass Confusion Over Slightly Misleading Nomenclature..."  ?

If this discussion is to continue could you please refrain from bringing it into the realms of personal attacks on another member. You are free to post whatever you like with regards how you think this specific term should be used and measured but constant digs won't be tolerated any more. 

[SteamyTea]

41 minutes ago, Sensus said:

21 hours ago, SteamyTea said:

You have to include conductivity as well. Do a dimension analysis on what you have done and you will see it does not make sense.

Yes. And this is why we have confusion like this.

 

It is not hard or difficult scientifically or mathematically, but by just giving things random names, or titles, or units, nothing can be worked out properly.

 

 

Yes, the analysis has to include thermal conductivity as well, but that's a separate factor, and I think needs to be kept separate, if only to remind people that you can have two thermal elements with the same U-value, but widely differing thermal mas (or thermal inertia... or whatever you choose to call it), and as a result they will perform differently in terms of transient thermal response.

Copied straight from good old Wikipedia, with minor editing to make it legible.

The main point is that thermal conductivity is very important and not a separate factor.

 

Thermal inertia[edit]

Thermal inertia is a term commonly used for modelling heat transfers. It is a bulk material property related to thermal conductivity and volumetric heat capacity. For example, "this material has a high thermal inertia", or "thermal inertia plays an important role in this system", mean that dynamic effects are prevalent in a model, so that a steady-state calculation will yield inaccurate results.

The term is a scientific analogy, and is not directly related to the mass-and-velocity term used in mechanics, where inertia is that which limits the acceleration of an object. In a similar way, thermal inertia is a measure of the thermal mass and the velocity of the thermal wave which controls the surface temperature of a material. In heat transfer, a higher value of the volumetric heat capacity means a longer time for the system to reach equilibrium.

The thermal inertia of a material is defined as the square root of the product of the material's bulk thermal conductivity and volumetric heat capacity, where the latter is the product of density and specific heat capacity:

 

I = (k.p.c)^0.5

See also thermal effusivity

• k is thermal conductivity, with unit [W m⁻¹ K⁻¹]
• p is density, with unit [kg m⁻³]
• c is specific heat capacity, with unit [J kg⁻¹ K⁻¹]
• I has SI units of thermal inertia of [J m⁻² K⁻¹ s^−1/2]. Non-SI units of Kieffers [Cal cm⁻² K⁻¹ s^−1/2] or [1000 Cal cm⁻² K⁻¹ s^−1/2] are also used informally in older references.^[5][6]

For planetary surface materials, thermal inertia is the key property controlling the diurnal and seasonal surface temperature variations and is typically dependent on the physical properties of near-surface geologic materials. In remote sensing applications, thermal inertia represents a complex combination of particle size, rock abundance, bedrock outcropping and the degree of induration. A rough approximation to thermal inertia is sometimes obtained from the amplitude of the diurnal temperature curve (i.e., maximum minus minimum surface temperature). The temperature of a material with low thermal inertia changes significantly during the day, while the temperature of a material with high thermal inertia does not change as drastically. Deriving and understanding the thermal inertia of the surface can help to recognize small-scale features of that surface. In conjunction with other data, thermal inertia can help to characterize surface materials and the geologic processes responsible for forming these materials.

Thermal inertia of the oceans is a major factor influencing climate commitment, the degree of global warming predicted to eventually result from a step change in climate forcing, such as a fixed increase in the atmospheric concentration of a greenhouse gas.

 

 

41 minutes ago, Sensus said:

I personally quite like ST's label of 'thermal inertia',  but whatever... I think we have to recognise that one or two random internet nerds aren't going to change what the rest of the industry calls it. We're stuck with 'thermal mass', whether we like it or not.

But if you are in a meeting about this, and you hear people using the incorrect term, and showing little understanding of the subject, one tends to loose confidence in them.

 

Edited September 8, 2019 by SteamyTea

[Jeremy Harris]

51 minutes ago, Sensus said:

On the other thread, JS makes the very clear statement that thermal mass does not exist as a parameter. IT DOES. It just doesn't have the name that JS would like it to have, because it uses the word 'mass' when - whilst relating to mass for its derivation - it isn't actually measured in units of mass.

 

He also stated that "Like all other supposed explanations for this mythical physical property, [someone else's practical definition of the term] fails because it doesn't define the units of measurement" and that " Thermal mass has no units, so how can anyone measure it, or define what is 'high' or 'low'?".

 

He asked me above - presumably expecting  me to be unable to answer - to state the units. I DID.

 

I also pointed him back at the very website he used himself to 'prove' his point, which also gives a definition for thermal mass that identifies its units... it's a definition you'll find, I'm sure, in any number of textbooks on the subject. Certainly (because I've just checked), I have it in my lecture notes from the Building Science lectures I took in the first year of my Architecture degree, three decades ago. This stuff is basic, and not at all new.

 

For someone who claims such great care for precision of nomenclature, I find it odd that he should be making these sorts of statements, or creating topics with titles like 'The Great Thermal Mass Myth".

 

Surely, by his own standards of accuracy, he should be renaming that topic "The Great Thermal Mass Confusion Over Slightly Misleading Nomenclature..."  ?

 

 

 

OK, I'm going to be very specific here, and ask again for the specific units of "thermal mass", as a property, as I cannot see anywhere in this thread where any valid units have been given.

 

As mentioned earlier, you gave two sets of expressions when asked this before, one I think was meant to be a unit for non-specific heat capacity per unit area, " For a thermal element, it's Kj/m²K ".  Correct me if I'm mistaken, but I believe that what was probably meant here was kJ/m²·K, kilojoules per m² · K.  This is a measure of heat energy per unit area.  There are no units of time, thermal conductivity, mass or volume expressed here, so how can that relate to either "thermal mass" or thermal inertia?  I think we are in agreement that time is a key element, in that what is trying to be described is the rate of change of temperature with respect to time, inside the house.

 

The other expression given earlier was non-dimensional heat capacity " For a building as a whole (albeit this needs to be treated with caution, as an entire building does not respond as one homogeneous and uniform element), it's simply Kj/K ".  Again I'm going to translate this into what I think was meant, which was kJ/K (kilojoules per kelvin).  If I've mistakenly interpreted this then please correct me.  This basic expression for heat capacity is not tied to any units of mass or volume, so cannot be used as it stands to determine how a building will respond to changes in temperature.  As before, it doesn't have any measure of thermal conductivity, mass, volume or time, either.

 

If we wish to try to define, and model, how a building will behave, in terms that I believe most people would find useful, we need to include time, as the key factor for comfort (which is really what we are trying to predict or measure) is how quickly the inside of a building responds to a change in temperature.  If someone chooses to give valid units for the generally used term "thermal mass", such that all the key parameters that define it are clearly expressed, then I'd accept it.  It does seem very clear that what many interpret as being the meaning of this term is the rate of change of temperature inside the house in response to either a step change in external temperature of a step change in heat input to the inside of the building, which can be determined easily from the thermal inertia.

 

[ToughButterCup]

7 minutes ago, Sensus said:

[...]

That approach screams 'inexperienced theoretician' at me... often someone who is trying to mask that inexperience, and their lack of practical understanding, with fancy words, hair-splitting, and complicated terminology.

[...]

 

To me, that's easily seen as an ad hominem attack . Please dont. Theoretician or not, that point has nothing to do with the core discussion..

[SteamyTea]

2 minutes ago, Sensus said:

The term isn't incorrect. It might not be quite as theoretically descriptive as 'thermal inertia', but it's a generally accepted term, and it is meaningful.

But totally missunderstood because people think it is the mass that is the key element.  That is like saying my Ford C-Max is more stable than a Ford Focus because it is heavier.

Total nonsense.

4 minutes ago, Sensus said:

As I said in my first post on the subject, it's simply specific heat capacity (a thermal parameter) multiplied by mass... Thermal Mass

Been answered.

5 minutes ago, Sensus said:

That approach screams 'inexperienced theoretician' at me

That is because you don't understand it too.  Sorry if that sounds personal, but no other way to say it.

[Jeremy Harris]

8 minutes ago, Sensus said:

 

The term isn't incorrect. It might not be quite as theoretically descriptive as 'thermal inertia', but it's a generally accepted term, and it is meaningful.

 

As I said in my first post on the subject, it's simply specific heat capacity (a thermal parameter) multiplied by mass... Thermal Mass.

 

Simples.

 

I have no problem with its continued use, and I certainly wouldn't lose confidence in someone because of it.

 

On the contrary: having a good grasp of the practical realities of both building construction and environmental design, I am very sceptical indeed of anyone who tries to define or analyse the factors involved with too much precision. That approach screams 'inexperienced theoretician' at me... often someone who is trying to mask that inexperience, and their lack of practical understanding, with fancy words, hair-splitting, and complicated terminology.

 

 

 

 

 

 

Heat capacity can be expressed either as a non-dimensional term, as heat energy, J/K, or as a dimensional term that includes either mass or volume, J⋅g⁻¹⋅K⁻¹ or J⋅cm⁻³⋅K⁻¹

 

Heat capacity multiplied by mass is just the mass heat capacity, and is not "thermal mass"

 

These units are well-defined, and in common use, and the expressions in the quote above are incorrect.

[SteamyTea]

3 minutes ago, Sensus said:

You don't need them to define thermal mass.

So what are you defining then, seems to be just mass, as without time, you cannot have any change.