House June warmth profiles: I

Graph of house temperatures versus height

Where is the warmth in a house?

People are building houses that should keep warm in winter with little heating.
Some parts of the house will stay warmer than other parts. Which parts? How warm?
Answers are not easily found. I hope this temperature record from a house with only personal heating may be useful. This was a time when the house was under extreme stress due to cold weather.

Over a five-day period in winter 2016, I read thermometers frequently at a number of stations around the house. I have selected those stations that form profiles from top to bottom of two wings of the house: the two-storied west wing, and the east wing that is one-storied with a clearstory.
To find how my house differs from yours, see the note below: “Key features of the house”.

Selected thermometer stations

In the West Wing (two-storied)

OUTDOORS, upstairs veranda (+4.7 metres);
Wall upstairs at head height (+4.2 metres);
Wall downstairs at head height (+1.5 metres);
Floor slab surface downstairs (0.0 metres);
Garden subsoil at -0.75 metres.

In the East Wing (single-storied)

Clearstory space at +3.5 metres;
Wall in the hallway at head height (+1.5 metres);
OUTDOORS, in a Gill Screen (+1.5 metres);
Floor slab surface in the en-suite (0.0 metres);
Solid “heat bank” beneath the floor slab (-0.75 metres).

Part I: Average temperature values

SUMMARY RESULT
In the ground under the floor slab the temperature would be just warm enough for winter comfort. Above the floor slab, the higher you go, the colder it gets.

Results

The graph above plots mean temperature against height above the floor slab. (The mean temperature is the time-average over the five days.)

Comparing east wing, west wing, and outdoors

The single-storied east wing was several degrees warmer at all heights than the two-storied west wing. The east wing has advantages: thermal mass, perimeter insulation in the footings, less shading, and a more compact shape.
Continue reading

Mirrors to reflect the sun

I have begun to warm the shady side of my house with reflected sunlight in winter.

Aluminium mirrors to reflect sun

Sun Mirrors Mar-17

This winter’s set-up.

The first photo shows the present temporary set-up, done on the 10th of March 2017. That is, soon after I had changed the house from its summer regimen (to keep cool) to its winter regimen (to keep warm).
As shown, I attached aluminium foil to the courtyard wall on the south boundary of my block. The foil forms mirrors that reflect winter sun onto the south wall of the house, the edge of the floor slab, the footings and some nearby concrete paths.
The mirrors are sheets of aluminium cooking foil (“Alfoil”) 300 mm wide, cut to 900 mm lengths. I attached the foil to the wall in vertical strips with double-sided tape. As the wall is 12.6 metres long, the total mirror area is 11.3 square metres.

Last winter’s set-up.

Temporary aluminium mirrors to reflect sunlight

Sun Mirrors May-16

Last year, during April and May, I attached only 17 strips of foil 700 mm long in the same way. The total area then was 3.6 square metres. In that winter, the wind did a little damage, which I taped over. Much worse damage was caused by a magpie-lark attacking his reflection. By October, they were torn as shown in the third photo.

Aluminium foil damaged by birds

Bird Damage Oct-16

I repaired some of that damage, too, using builders’ foil, which is stronger. Early in November 2016, I removed all the foil. By then I wanted shade. not sunlight.

Effect of the mirrors

The white-painted courtyard wall reflects nearly all the sunlight it receives. However, this is diffuse reflection, going equally in every direction. Only a small part of it goes to points likely to warm the house.

Sunlight that has been reflected towards the house.

Reflected Light May-16

The aluminium foil reflects in a specular (mirror-like) way, sending nearly all of the solar energy downward at the same angle that it arrived. Because the foil is wrinkled, these mirrors spread the beam of sunlight out to about twice the width of the mirror surface. It is still quite concentrated as can be seen in the last photo, which is lit mainly by reflection from the foil.

Light reflected from these aluminium mirrors is not aimed precisely at points where it would best warm the house. The mirrors are not mobile, and their location owes a lot to chance. Furthermore, the house shades the mirrors for parts of each day; different parts as the season changes.
However, I think the warming effect will be useful, and I hope to be able to measure it.

Related Topics

The mirrors are part of the Courtyard that I have described in posts and pages listed in “My House Page”.


I raised the question of mirrors to reflect sunlight in a thread titled “Reflective Film” on a forum of the Alternative Technology Association (Melbourne).

Constructing My Solar-passive House

Photo of tossing a brick

One Brick Thermal Mass

The “Indoor climate” posts on this blog relate to the particular house that I live in. Mainly by luck, it has proved to need very little energy indeed to remain comfortable in all seasons.
Recently, I have collected and arranged photos of the house so that people can see what kind of a house it is.
These photos are accessed by way of “My House Page”.

House footings on a rise

Footings View East

In the last few days I have uploaded photos of the stages in the building of the house. They are in two galleries. The first, “Building Photos: Start” covers from preparation for building up to the erection of timber frames. The photo on the left, showing some of the footings, is an example.

The second new gallery, “Building Photos: Finishing” covers from laying bricks for thermal mass walls (as in the photo at the top) to the completion of an acrylic textured coating on the walls.

Photos of the completed house, inside and out, had been posted already, in “Award photos 1999”.

Once an “Indoor Climate” post or page has been accessed on this web-site, links to all others appear. A post such as this one, when accessed through “Home” will not link to the others until it is selected positively by clicking its title line.

My Solar-passive House Photos and Details

 

A plan of the house

Monash Street House Plan

Distant view from the south-east

Distant view from the south-east

Posts on “Indoor Climate” in this blog come from my experience living in my solar-passive house from 1999, and monitoring its performance.

Until now, I have not given readers a clear idea of what the house is like. I have now set up a special page called “My House Page” where details can be found. So far, there are two sub-pages, both referring to the time when the house was new:

  • A gallery of photos called “Award photos 1999”, and a house plan, which were submitted in an entry for the Housing Industry Association (NSW) awards for 1999.
  • An essay “House Profile 1999” that sets out the principles that I thought important then, and the features that I had built in to the house. I added a reading list of books available at that time, and a list of Credits to those people who built the house.

Navigation

The “My House Page” is not directly indexed in the main menu on the banner, but it appears with a hover over “Indoor Climate”.

Posts and Pages on Indoor Climate have links to each other in the side-bar on the right, in the panel “Indoor Climate Blog and Pages”. This panel does not appear on the Home Page, but only when an “Indoor Climate” blog post (or Category of posts) is selected.

I intend to add more pages in time.

Managing my low-energy house: II. Features needing attention

Photo of clear-story area with winter sun and a fan

Clear-story fan set for winter

This post, and the companion post I. Features needing no attention were posted originally to a forum of the Alternative Technology Association (See Note below.)

My low-energy house at Manilla, NSW, maintains year-round comfort in a climate of daily and seasonal extremes. In the climate classification of the Building Code of Australia, it is in Zone 4: “Hot dry summer, cool winter”, along with Tamworth, Mildura and Kalgoorlie.
This house differs from most houses in relying on the design of the house to achieve comfort, with hardly any energy needed for heaters or coolers.
There is little artificial control: the “home automation system” consists only of timers set twice a year. Some of the comfort features call for daily action in certain seasons. However, these simple daily chores could have been avoided by small changes in the design. [But see “Note added 2016.”]

The success of the house in maintaining comfort in all seasons is shown by scatter-plots of daily indoor and outdoor maximum and minimum temperatures over a period of three years.

Features re-set twice a year

Dates for re-sets

For part of each year, the Manilla climate is too hot for comfort, and for the rest it is too cold. Some house features are re-set twice a year, making a “winter regimen” and a “summer regimen”. At first, I set the change-over dates near the equinoxes, 20th March and 22nd September. For simplicity I changed on 1st April and on 1st October. Later, I found it better to change on 1st March and 1st November, because the time when the climate is too hot is shorter than the time when it is too cold.

Motorized curtains

Curtains fitted to five north-facing windows, and a shutter fitted to a sun-porch window, should be opened to admit winter sun and closed at night to trap the heat. In summer they should be closed by day to keep out radiant heat and opened at night to allow heat to radiate out. The curtains and the shutter have motors controlled by a programmable timer (at lower right in the photo). In autumn (1st March), the timer is set to open at 07:40 and close at 17:20 daily. In spring (1st November) the timer is set to open at 18:00 and close at 06:00 (Standard Time).

Clear-story windows and fans

Continue reading

Managing my low-energy house: I. Features needing no attention

Photo of sunlit house interior

July sun heats the house

This post, and the companion post “II. Features needing attention” were posted originally to a forum of the Alternative Technology Association (See Note below.)

My low-energy house at Manilla, NSW, maintains year-round comfort in a climate of daily and seasonal extremes. In the climate classification of the Building Code of Australia, it is in Zone 4: “Hot dry summer, cool winter”, along with Tamworth, Mildura and Kalgoorlie.
This house differs from most houses in relying on the design of the house to achieve comfort, with hardly any energy needed for heaters or coolers.
There is little artificial control: the “home automation system” consists only of timers set twice a year. Some of the comfort features call for daily action in certain seasons. However, these simple daily chores could have been avoided by small changes in the design. [See “Note added 2016” below.]

The success of the house in maintaining comfort in all seasons is shown by scatter-plots of daily indoor and outdoor maximum and minimum temperatures over a period of three years.

I. Features needing no attention

Heat transfer to and from the heat bank

The mass of concrete, bricks and rubble under the concrete floor slab is edge-insulated with foam to a depth of half a metre to prevent heat leaking sideways to and from the surrounding soil and subsoil. This 150 tonne edge-insulated under-floor mass is a “heat bank” which absorbs and yields heat so slowly that it holds the same temperature (at 750 mm depth) within a degree for weeks at a time.
Double-brick walls (17 tonnes) inside the house, and the floor slab itself (28 tonnes), are also parts of the heat bank. Their exposed surfaces (See photo.) absorb heat from sunshine (and yield heat to cool flows of air) so as to spread heat (or coolness) around the rooms. Within each day they conduct heat to and from the rooms of the house, and from room to room. They then conduct heat slowly to and from the under-floor mass.
In the absence of the house, the under-floor mass would have the same temperature as the subsoil of the area. A thermometer at 750 mm in the subsoil near the house shows a 14.6° yearly temperature range, from 12.9° to 27.5°. Even an ordinary light-weight, poorly-insulated house built on a concrete slab on the ground here would be made more comfortable by these stable subsoil temperatures. Midsummer and midwinter temperatures in such a house (next door) are plotted here and here.
It is clear that temperatures in that conventional house vary much less than outdoor temperatures, and remain close to that of the subsoil. The heat bank under my solar-passive house has an even more stable temperature than that of the surrounding subsoil. (There is a graph showing one year of heat bank and subsoil temperatures here.)

Insulation

Thermal insulation reduces the flow of heat in and out of the house. With sufficient insulation, the heat of the day is replaced by the cool of night before the house becomes too warm. Insulation improves comfort permanently. Continue reading

Geoff’s solar-passive house at Manilla

View of solar-passive house

Geoff’s solar-passive house

A second high-mass solar-passive house was built in 2009 at Manilla, within 300 metres of mine.
My friend Geoff designed his house and used the same builder that I did. Sadly, after five comfortable years in his house, Geoff has passed away. Thanks to his daughter, I can show you the features of the house.
Thermometers, and power bills show that its performance is similar to mine. That is to say, it is very successful!

In Manilla’s climate of daily and seasonal temperature extremes, Geoff rarely needed to use his low-powered reverse-cycle air conditioner.

Plan of solar-passive house

Strafford Street solar-passive house: plan

Specifications

Dimensions

Length, East-West:     18.28 m
Width, North-South:    9.45 m
Ceiling height:               2.70 m

Area

Room area, Living/Kit/Bed 1/Study:      115.9 m^2
Room area, Bed 2:                                    13.8 m^2
Room area, Bed 3:                                    14.1 m^2
Room area, Bathroom:                              8.6 m^2
Room area, Laundry/Darkroom:               7.7 m^2
Area of walls:                                             12.7 m^2
Total House Area (without patio):       172.8 m^2

Exterior walls

North wall: double brick
East, west, and south walls: 90 mm stud, including 9.61 m reverse brick veneer
Cladding of stud walls: custom orb (horizontal)
Cladding of gable ends: plain roofing panels with 50 mm foam

Interior walls

Single brick:    17.16 m
Stud wall:        11.66 m

Windows (and two glass doors)

All double-glazed 3/6/3 in uPVC frames
(North-facing window area is 16% of the floor area of the house.)
North-facing:           27.00 m^2 (76%)
East-facing:               3.84 m^2 (11%)
South-facing:            4.50 m^2 (13%)
West-facing:             0.00 m^2 (0%)
Total:                      35.34 m^2 (100%) Continue reading