Pros and Cons of PH

[LA3222]

1 hour ago, joe90 said:

@Mako you are about to get a lecture ? (On the other hand I am a fan of a “heavy house” and built mine that way).

Don't think a lecture will be forthcoming on 'thermal mass', a lot of the protagonists who would 'bite' on this topic seem to have disappeared from the forum. Where is @Jeremy Harris nowadays?

[the_r_sole]

I like passivhaus as a concept and was planning on doing my certification this year but missed out...

However if it was my own house I wouldn't adopt the full standard as there are definitely compromises i would make for my own preferences, i think you need to figure out why you want passivhaus (if you do) and then work backwards to understand whether you need to achieve the certification 

[epsilonGreedy]

33 minutes ago, LA3222 said:

Where is @Jeremy Harris nowadays?

 

 

Not sure, I saw a similar question posted on the Tesla car forum.

[epsilonGreedy]

34 minutes ago, the_r_sole said:

However if it was my own house I wouldn't adopt the full standard as there are definitely compromises i would make for my own preferences

 

 

I would not want to live in the most highly performant of Passiv homes because I feel the temperature stability achieved by these examples is not good for human health. I think a bedroom should shed a few degrees over the course of the night and 21 degrees is too warm downstairs before 2pm or 6pm.

 

In evolutionary terms we are still neolithic hunters adapted for diurnal temperature fluctuations, hence Passiv homes confuse our biology. In other aspects of modern life people are discovering the benefits of recreating neolithic privations e.g. the 5:2 diet starvation which mimics those occasions when the hunting party failed to spear the wooly mammoth and the tribe went hungry that night. Other new age diets recreate seasonal surpluses and deficits in food groups.

 

My hunch is that within 20 years similar lifestyle concepts will have worked their way into passiv home control systems and people on buildhub will be raving about the health benefits of selecting cave mode or hawaiian reed hut mode.

[scottishjohn]

 

mine build style   is simple -

I like a house that is a constant temp  and dress to suit it if it gets too hot -- not wear lots of jumpers inside - window open at night for bedroom 

the idea of lots of insulation round outside of a solid concrete heat sink is a good one for my way of thinking 

the concrete -thermal mass- slows down any temp  change

 If I want to get cold I can go walking outside  in the countryside --having a draught  in the house -- no thanks 

[joe90]

That’s my philosophy as well and mine works just fine, soon to work out about E7 and use the mass of the house to store cheaper heat.

Edited October 1, 2020 by joe90

[Simplysimon]

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Edited October 1, 2020 by Simplysimon
duplicate post

[Simplysimon]

8 hours ago, Mako said:

The question is, why warm cell blown? What are the benefits?

timber kit is a quick build method to get to the watertight stage, can be built in in parts in a workshop, knocked down, taken to site and erected or stick built on site with a tape, chopsaw and a nailgun. 350mm blown cellulose gives you 0.1 of a u value and is a heavy build due to weight of i beams and cellulose pumped to 55kg/m3. i do appreciate it's not as heavy as blockwork but when you glue the sheeting to both faces inc. joints and seal around windows and to floor, you should, as previously stated by @Nickfromwales, easily achieve a low air pressure test. there is also evidence of very good sound reduction with cellulose. no gaps/cold bridges in the filling due to being blown under high pressure. oh, and you can insulate it yourself. low carbon as well as it's fixed in the timber and paper, board material..............

 what are the benefits of blockwork/icf? ☺️

any idea which method i'm using?

[scottishjohn]

and with isotex/durisol etc you can stop start if you really have to -- nothing that water will damage 

 

we all make our own choices

[SteamyTea]

3 hours ago, Mr Punter said:

Why do you think this will be the case?

I am of the view that as renewables, mainly wind and solar are now the cheapest energy source to deploy, and still getting cheaper, there is no need for energy costs to rise above their current level of around 5% of median household income.

[SteamyTea]

3 hours ago, LA3222 said:

Don't think a lecture will be forthcoming on 'thermal mass', a lot of the protagonists who would 'bite' on this topic seem to have disappeared from the forum

Don't change the physics though.

2 hours ago, epsilonGreedy said:

I feel the temperature stability achieved by these examples is not good for human health. I think a bedroom should shed a few degrees over the course of the night and 21 degrees is too warm downstairs before 2pm or 6pm.

 

In evolutionary terms we are still neolithic hunters adapted for diurnal temperature fluctuations, hence Passiv homes confuse our biology.

I have lived in places where the temperature hardly changes seasonally, let alone diurnal, as have many millions of others.

[Thedreamer]

I've been on here for few years, seen this discussed, my observation is that is not that some architect gave it the thermal mass name?

 

What people really want is material that hold heat, whatever that term is?

[SteamyTea]

14 minutes ago, Thedreamer said:

What people really want is material that hold heat, whatever that term is

All materials hold heat, and all have thermal conductivity.

It is the product of the two that is important, as well as the shape they are formed into.

Then you have to take into account mass and volume, and the practicalities of using those suitable materials.

[ProDave]

Thermal Capacity is the term you are looking for.

 

Decrement delay is another important parameter, which is basically a measure of how fast heat passes through.  Insulation like glass wool, wood fibre, blown celulose etc have a long decrement delay where PIR type insulation has a much shorter decrement delay.

[the_r_sole]

In my future house I'd like a grundofen type of fire (also heating ufh) and a twin stud construction with blown cellulose insulation

[Thedreamer]

12 minutes ago, SteamyTea said:

All materials hold heat, and all have thermal conductivity.

It is the product of the two that is important, as well as the shape they are formed into.

Then you have to take into account mass and volume, and the practicalities of using those suitable materials.

 

My device which should not be named, is burning away at the moment. It's surrounded my 6inch dense concrete blocks and in the two nights I have had it on the blocks have held the heat well and the temperature is perfect in the morning.

 

If we didn't have these blocks then I would imagine we would get a hotter room just now and then a colder temperature in the morning.

 

Is this not what is trying to be achieve with folk who use the sunlight with thermal mass. Can somebody just give it a new name! 

[Thedreamer]

7 minutes ago, ProDave said:

Thermal Capacity is the term you are looking for.

 

Decrement delay is another important parameter, which is basically a measure of how fast heat passes through.  Insulation like glass wool, wood fibre, blown celulose etc have a long decrement delay where PIR type insulation has a much shorter decrement delay.

 

Ok, thermal capacity. 

 

How come people just don't use this term instead?

[epsilonGreedy]

1 hour ago, SteamyTea said:

I have lived in places where the temperature hardly changes seasonally, let alone diurnal, as have many millions of others.

 

 

A cornish tin mine?

[Dan F]

11 hours ago, Mako said:

Based on my read many members are underestimating the benefits.

solar gains, storage, and heat release when required without any input. Why is that not a benefit? Surely it saves 

energy for heating/cooling.

 

I think the correct technical term for what you describe is "Specific Capacity" whhich is meansured in Wh/K.  PHPP agrees with you that the higher the specific capacity of a constuction, the lower it's overall heating demand.

 

If I take our PHPP and increase the specific capacity from 84 Wh/K (concrete slab + timber-frame) to 180 Wh/K (suggested value for a concrete walls too) this is what happens:

- Heating demand goes down 5%

- Heating load stays the same.

- Overheating risk goes down by 15%

 

We are dealing with overheating via use of external blinds so that a non-issue, and 5% reduction, in an already very low, heating demand wouldn't be enough to justify a concrete structure in my opinion anyway, given the sustainability and sound-insulating attributes of timber frame and warmcell alternative.

 

 

[Mako]

8 hours ago, scottishjohn said:

having studied both very close and looked at samples -but not built with either

the main difference between the the 2 would be a finer finish and accurate width dimension on the istoex when compared to durisol

 durisol you can only be sure to have one side totally flat due to some differences in thickness of blocks , length and height dimensions seem to be accurate though --not a great problem really 

 and the other difference is the concrete core is 120mm on isotex and 150mm on durisol if I remember correctly - so a  25%saving on concrete costs -

check yourself in case things have changed

thanks john, am i right thinking that more concrete you have in the building the better?

if the concrete is accessible as a thermal mass?

[Mako]

6 hours ago, LA3222 said:

Don't think a lecture will be forthcoming on 'thermal mass', a lot of the protagonists who would 'bite' on this topic seem to have disappeared from the forum. Where is @Jeremy Harris nowadays?

i would love a lecture, but so far using common sense 

[Mako]

1 hour ago, Dan F said:

 

I think the correct technical term for what you describe is "Specific Capacity" whhich is meansured in Wh/K.  PHPP agrees with you that the higher the specific capacity of a constuction, the lower it's overall heating demand.

 

If I take our PHPP and increase the specific capacity from 84 Wh/K (concrete slab + timber-frame) to 180 Wh/K (suggested value for a concrete walls too) this is what happens:

- Heating demand goes down 5%

- Heating load stays the same.

- Overheating risk goes down by 15%

 

We are dealing with overheating via use of external blinds so that a non-issue, and 5% reduction, in an already very low, heating demand wouldn't be enough to justify a concrete structure in my opinion anyway, given the sustainability and sound-insulating attributes of timber frame and warmcell alternative.

 

 

thank you for correcting my terms, im not an expert, im trying to decide which method to use to build my next house.

what happens if you use concrete in walls and suspended floors? if i understand your calks you converted walls only

 

do we anticipate heating  the concrete mass by solar gains in the winter?

I believe the heating load should reduce as well, am I wrong thinking that?

 

sound proofing, I thought soundproofing is also improved by concrete, living in timber frame house now, I can hear everything

through the walls.

 

sustainability point of concrete v timber, if you look at the life span of timber frame builds being around 50years, concrete buildings

are here already for hundreds of years. surely concrete must be more sustainable compared to timber. 

 

[Mako]

4 hours ago, Simplysimon said:

timber kit is a quick build method to get to the watertight stage, can be built in in parts in a workshop, knocked down, taken to site and erected or stick built on site with a tape, chopsaw and a nailgun. 350mm blown cellulose gives you 0.1 of a u value and is a heavy build due to weight of i beams and cellulose pumped to 55kg/m3. i do appreciate it's not as heavy as blockwork but when you glue the sheeting to both faces inc. joints and seal around windows and to floor, you should, as previously stated by @Nickfromwales, easily achieve a low air pressure test. there is also evidence of very good sound reduction with cellulose. no gaps/cold bridges in the filling due to being blown under high pressure. oh, and you can insulate it yourself. low carbon as well as it's fixed in the timber and paper, board material..............

 what are the benefits of blockwork/icf? ☺️

any idea which method i'm using?

my only worry with that system is due point reaching into the cellulose layer and creating condensation issues, mould growth, etc

how is the cellulose dealing with that?

speed i take your point, but building timber frame in this climate/humidity is challenging to keep the timbers dry as soon as they come out from the factory the humidity is at it. by the time you get it watertight its too late. i know i live in timber frame house and i swore never again.

constant movement 2 a year a need to go around and fix cracks and decorate. i also read somewhere that air-tightness is compromised

after some time when the membrane joints start failing. don't get me started on PIR insulation not fit for purpose.

sorry for the moan im fed up with this house.

as the blockwork doesn't deliver either, the only option is concrete, unless you know another alternative.

 

[Mako]

5 hours ago, scottishjohn said:

 

mine build style   is simple -

I like a house that is a constant temp  and dress to suit it if it gets too hot -- not wear lots of jumpers inside - window open at night for bedroom 

the idea of lots of insulation round outside of a solid concrete heat sink is a good one for my way of thinking 

the concrete -thermal mass- slows down any temp  change

 If I want to get cold I can go walking outside  in the countryside --having a draught  in the house -- no thanks 

i think we are on the same page... i don't think that strictly speaking PH needs to be of 21'C, i think you can control the temperature,

in a concrete house if you wish. design it for 18'C and when need it put a jumper on.

my wife's preference is 25C all year round

[Ferdinand]

1 hour ago, Mako said:

thanks john, am i right thinking that more concrete you have in the building the better?

if the concrete is accessible as a thermal mass?

 

One issue there is that you need to think about time factors in heating up and cooling down, and balance the amount of heat the house can hold with the rate at which it can get in or out.

 

If you have a lot more thermal storage in the extra concrete inside your superinsulated airtight house, then the larger amount of stored heat will escape very slowly once it has built up - and you could have a high swing that eg stays high for a number of days 'cos your insulation is keeping it in. The total amount of heat moved by air is relatively small.

So things like the "decrement delay" (which is a measure of how long heat takes to soak through your walls) become more important. If it takes (say) 12 or 16 hours, that means that it will be a long hot day before the inside starts heating up, and much of the heat can go back out of the walls outwards overnight, plus you can cross ventilate, stack ventilate or purge ventilate.

 

Mine is *not* superinsulated, and in hots circs it can get uncomfortable by early to mid afternoon, so in a real heatwave (outside temp say 30C or more for several days) I need to have my skylights and a downstairs window or two open overnight, and have it all shut it all up before the sun comes out.

 

One slightly unintuitive thing some here have found is that overheating through windows in highly insulated houses is that overheating can be more of a problem in spring / autumn than in summer. That is because we are used to doing things like brise soleil and similar things now, but even though the slanted sun in the spring / autumn is less intense, it circumvents the measures we think to put in for the summer sun by being lower.

Ferdinand

 

Edited October 2, 2020 by Ferdinand