Hi Natasha.

Your double brick house probably has more thermal mass than mine. Since you are letting in warm air during hot days, does your house get cool enough at night?

I just had two days here of max over 40 deg on the open back porch. In seven summers I have registered 17 days over 40 deg, making about 2.5 days per year. This summer has three over 40 so far. Summer 03/04 had the most days over 40: six days, including my record of 41.9 deg. There were no 40 deg days in 01/02 or 04/05.

My new screen is reading daily summer maxima about a degree higher than the porch, but the porch readings don't seem to be too bad.

Thursday Feb 2 was a very trying day. My screen max was 41.8, but more remarkable was the temp when I arrived home at 21:30: 35.5 degrees! Inside the house was 30.5, which seemed very cool until I got used to it. Overnight DP's at Tamworth hovered about 15 deg. As usual, I didn't open the windows until the temp outside dropped below the temp inside. That happened at 03:30, at 29.5 deg! The overnight minimum outdoors was 25.9, and indoors 28.1.

Today you might call a perfect day!

This morning the minimum was a brisk 7 degrees, and it was calm, with no wind and no clouds. By noon it was 25 degrees, and it is likely to stay above that figure until sunset, without going over a very comfortable 28 degrees. It is sunny, with a light breeze.

A day like this calls for something rare in my house climate management: open everything up during the day!

During the summer half-year the house is shut up and curtained during the day to keep out the radiation and hot air. Most days in the winter half-year the house air temperature is higher than the outdoor temperature, so the house is kept closed to keep the cold air out. The windows let in the sun, though.

Today the indoor temperature started at 21 degrees. If I kept the house shut as usual it would probably go to only 25 degrees. Now that I have opened all the doors and windows, I may get it up to 27 degrees.

Every bit of heat I can store now in the brickwork and slab helps to keep the chill out in July and August.

Is this a record? :wave:

This morning's screen minimum was -1.6 deg, but the indoor minimum in the core rooms of the house was 19.9 deg. That is, the (unheated) house was 21.4 deg warmer than outdoors.

I wonder if values as high as this are often achieved anywhere. Where climates are more extreme, there are no unheated houses.

My attached double garage, which behaves much like an ordinary slab-floored house, was 12.6 deg warmer than outdoors.

mostly the humidity and warm temps.With them combined can make some very uncomfatble heat indexes much more uncomftable than further inland.record heat index here is 52c so thats why i use air con.average temp at my place for the summer months is over 30c and i still get coastal humidity here.january had a average min of 22c aswell so it dosent cool down.I recorded 7 days of 35c or just below in jan alone this year.

EDIT
also my house is east/west facing so picks up the brunt of the summer sun

well its been cold here lately and the house temp is holding up fairly nicely, after those days of 30 - 35C inside its now sitting on 16 - 17 most of the time, still a few degrees to b winter in the house yet..

gets down to about 12-14c in my house most nights depending on outside temp.

my insulation must b better!! lol, whats it been for your outsdide temp latelyt?? been max's of around 15 and mins of around 5 - 10 :p

my max's are much warmer rarely below 20c up to 26c the other day mins of between 2-13c.I have woodern floor so the cool air just comes up through the floor boards at night

Percy and boardrider, both of you live much nearer the sea than I do. Daily temperature range here is about 16 deg. Yesterday went from 20.4 to 1.7. In the house there was only a 3.4 deg range: from 22.9 to 19.5.

I think slab-on-ground floors are better everywhere on the mainland south of Brisbane. Inland its hell without a slab.

boardrider 17, I am embarrassed to find I don't know how heat index is calculated. I think there was a thread about it.

Can anyone give me the formula?

I have a weather station hooked up to a pc and the program does it for me.It was around 37c and 60% humidity for 51c im sure ive got higher but my records always get wiped because of windows rebots DAM WINDOWS crashing lol
i think i got close to 60c heat index after a shower on a stinker day

LINK HEAT INDEX CALCULATOR

Thanks boardrider, for the calculator.

I found the actual formula at this Illinois State Academy of Sciences site:

http://www.il-st-acad-sci.org/kingdom/geo1013.html

It is:

"Heat index (HI), or apparent temperature (AI) = -42.379 + 2.04901523(Tf) + 10.14333127(RH) - 0.22475541(Tf)(RH) - ((6.83783 x 10-3)(Tf2) - ((5.481717 x 10-2)(RH2) + ((1.22874 x 10-3)(Tf2)(RH)) + ((8.5282 x 10-4)(Tf)(RH2)) - ((1.99 x 10-6)(Tf2)(RH2))

Note: In order for the Heat Index formula to work correctly, you must use the relative humidity in percent form. In other words, if the relative humidity is 65%, use 65 for RH in the formula, not .65."

The formula has lost its formatting, of course. Numbers should be superscripts meaning "to the power of" where they follow "10" or "Tf" or "RH".

no probs.

have fun with it

I realise now that the formula quoted is not for Celsius degrees. Wikipedia gives two Celsius formulae, but I can't use them. The simpler one involves vapour pressure which
A. I don't have, and
B. the units are not stated.

The other formula is so complex they have given it in 4 x 4 matrix form. That's a bit beyond me.

So I'm stumped there. I wanted to make a detailed spread-sheet so I could get accurate values.


I found a Celsius table of Heat Indexes here:

http://www.msc-smc.ec.gc.ca/cd/brochures/humidex_table_e.cfm

No wonder I like the climate where I live!
Heat Indexes at my place hardly ever get to 40! Not often even 36.

ah ok so its worse here.So i guess you can see why i use the aircon a bit more here than you do where its alot drier.Also i guess with the higher humidity my nights would be a lot warmer aswell

Right.
I wonder whether there are stats for heat indexes for stations.

BoM does give the formula for heat index here:
http://www.bom.gov.au/info/thermal_stress/#factors

They suggest getting values for stations by using daily max temp and 3 pm RH.

ah ok i never looked at the BOM for that

My house performance this winter is a bit disappointing. Quite a few mornings are below 18 deg indoors.
The house is not getting enough solar radiation. Sunlight on the floor slab and internal bricks should not only warm the indoor air, but also add heat to the sub-soil heat bank. It is adding less heat this winter than last winter.
The thermometer 750 mm under the slab never got below 17.6 last winter, and that was in mid-August. This winter it got down to 17.0 on 26 July. It is still only 17.1. This temperature is important, because in cold weather heat can (and does!) come back up from the heat bank whenever the temperature indoors gets below the temperature of the heat bank. Of course, that lowers the temperature of the heat bank, reducing the "balance of account".

I thought the low sub-soil temperature under the house might be due to low sub-soil temperature everywhere. There is insulation around the footings, but heat could leak through. This is not the case. The sub-soil temperature in the garden (at 750 mm) is about a degree warmer this winter than last winter. This day last year it was 12.9: today 14.1. Last winter the heat bank ran about 5 degrees warmer than the outdoor sub-soil; this winter only 3 degrees warmer.
I have managed the house (curtains, doors etc.) the same in both winters. I believe there must simply have been less solar radiation available to be used this winter. Unfortunately, I don't have access to solar radiation data, either at my house or from the Tamworth METAR.