Energy Design
The concept of 'sustainable holiday home' seems an oxymoron..
However, the clients are restoring a building that has been vacant for the past 10 years. And though the Villa will be used as a holiday home, it will also be rented out as much as possible during the rest of the year, and one day the Villa will likely be the client's permanent home.
So, how sustainable can we make this Villa?
For us, sustainability is firstly and primarily about reducing the amount of energy used in the Villa. And, then ensuring that the energy that is needed is produced as sustainably as possible. If the 'Villa' can make all the energy it uses it will technically become a 'zero' energy home.
Major users of energy in a home are heating and cooling, followed by hot water use in the kitchens, bathrooms and laundry, followed by refrigeration, washing machines, and, lastly lights.
(These days, actually the major energy user in a home is the smart-phone.. but that's another long and involved story.)
Heating and cooling
Passive options
Our heating and cooling strategy is to firstly examine the passive heating and cooling options that use the local weather conditions (such as prevailing hot and cold winds) and which works with the Villa's architecture, and which also calls for living in the Villa in a way that aligns with it's natural internal micro-climates.
Passive heating and cooling options:
The Villa is between a Mediterranean climate near a lake, and near the Swiss Alps. Temperatures range from summer heat waves of +38oC to snow and below zero night time temperatures in winter. There is a predictable breeze that blows a warmer air up the valley in the mornings and cooler air down the valley again in the late afternoon/evenings. This cool night breeze was traditionally used by locals in the area to cool houses at the end of summer days to prepare them for the next day's heat gain.
In summer the days are long and direct sun hours on the Villa are substantial. However, in winter the direct sun light hours are quite short. The direct winter sun hours are even shorter for the Villa as it is located such that mountains shadow the house till mid morning and from mid afternoon. For the shortest winter day the Villa has direct sun exposure only between 11am and 2pm.
Villa's architecture.
Built around a massive rock wall structure....
The villa is built with massive rock walls. The central rock wall separates the sun exposed south from the winter wind exposed, cooler north of the villa.
The neighbour's house attaches directly to the Villa on the west.
We suspect that under the plaster, the massive interior wall of the villa is built from rocks as for this ruin in the area. This provides a massive thermal mass that is shaded from the sun most of the time. This massive rock core keeps the house within a temperature range which is cool in summer, but which can be too cool in winter.
We collected temperature information for the Villa, however, this information is difficult to interpret as the Villa is currently essentially an open structure. Several windows on the ground and 1st floor are broken, most windows on the 2nd floor were never installed, and many doors to the ventilating staircase are missing. In addition the attic and cellar are open to the outside and open to the ventilating staircase. Thus currently (and for the last 10 years) the Villa has essentially been open to the elements. And the internal temperatures reflect these conditions.
We can however use our collected data and knowledge of thermal mass to predict the likely micro-climates in zones of the Villa once windows and doors are repaired and air flow in the house can be better controlled.
Passive House use
None of the holiday houses in the region are heated when vacant. Though the temperatures in winter are sometimes below 0C, the air is dry and the massive stone wall core in the villa moderates the internal temperature.
What is needed in vacant holiday homes over winter is to keep water in the pipes moving to stop it freezing and bursting pipes. Thus pumps for central heating systems are kept on low to keep the water in flow, and water taps for kitchens and bathrooms are allowed to drip. Only in houses higher in the mountains is water in pipes in central heating kept at ~5C to prevent freezing.
Vacant holiday homes are however ventilated in Spring (by opening windows) to increase air flow to prevent any potential condensation issues. Spring air that creeps into houses is warmer than the winter cooled surfaces inside the house. As warmer air can hold more water than colder air, this water can condense on to the colder surfaces in the house. This is easily prevented with air flow.
Most energy savings can come from heating and cooling the villa passively, that is, without technical equipment; using the architecture of the villa, the sun, the prevailing winds, and the constant ground temperature to make the villa interior comfortable, and by installing suitable insulation (such as double glazing, curtains and external shading) from the hot and cold.
How the house is used can impact how much heating and cooling is needed.
The house is naturally warmer and cooler in different sections.
Using the various climate zones for the appropriate behaviour will reduce heating cooling needs. For example, sleeping in cooler rooms in summer, and hanging out and entertaining in naturally sunny and warmer rooms in winter.
We propose using the Second Floor as the winter floor of the house. This floor has fantastic views, smaller windows
1. Use the naturally cooler parts of the house in Summer. - North side of the house. And close these off to the warmer South side of the house.
The coldest rooms in the Villa in Summer are the Ground Floor kitchen and living rooms.
The ground floor living room gets very little (if any sun) and has a uninsulated concrete/tile floor that sits directly on the ground. It is thus the coldest room in the house.
The coldest bedrooms are on the north side.
The ground floor living room gets very little (if any sun) and has a uninsulated concrete/tile floor that sits directly on the ground. It is thus the coldest room in the house.
The coldest bedrooms are on the north side.
2. Close shutters where the sun shines on the Villa. (East side in mornings, South side rest of day)- this gives external shading and prevents sun’s rays entering the Villa and prevents warming thermal mass inside (interior floors and walls). Sun rays hitting thermal mass warms the house more and stays in the house longer, than warm air flowing through the house.
3. Close windows if the outside air temperature is uncomfortably high. Remember, air flow gives perceived comfort even if the temperature of the air is high. ala sitting under a fan. Still air feels hotter than moving air.
4. Let warm air exit the house from up high and be replaced with cooler air where possible. Allow warmer air to flow up the stair case (open doors to stairwell) and out the top stair case window/attic and let replacing air enter from shaded north side windows close to/at/below ground level (e.g. cellar preferably via ground pipe air; ground floor north side windows/doors in kitchen and living room).
5. Ground Pipe
>50m, 50cm diameter ground pipe laid >1.5m underground will give air flow into the house that is ~15C. The length and diameter of the pipe allows ventilating air to flow slow enough through the pipe to let it equalise with the ground temperature, which at 1.5m underground is stable ~15C.
>50m, 50cm diameter ground pipe laid >1.5m underground will give air flow into the house that is ~15C. The length and diameter of the pipe allows ventilating air to flow slow enough through the pipe to let it equalise with the ground temperature, which at 1.5m underground is stable ~15C.
6. Open/reopen windows during the night to let house cool down with cooler night breezes that typically come down off the nearby mountains.
Experimenting insulation with wasted textile
