GB2356045A - Energy saving ventilation in buildings - Google Patents

Abstract

An integrated system for saving energy and passively collecting solar heat gains in buildings reduces heat loss through glazing both by trapping cold air between glazing and insulating panels or shutters so preventing room air from convecting against the shuttered area of glass, and by admitting fresh air to ventilate the building at the head of glazing and constraining it to flow downwards over the inner glass surface. Sustainable heat is extracted by cooling outgoing stale air to below external temperature with an air to water heat pump. The warm water produced may be circulated through a container serving as a combined hydronic "radiator" and solar panel fitted between two window shutters, the innermost being raised to transfer heat to the room. The outer shutter may be raised to allow the solar panel function of absorbing radiant solar energy towards heating domestic hot water.

Description

2356045 Energy Saving in Buildings

Background

This invention relates to the heating and ventilation of buildings, especially dwellings.

The likelihood of causing climate change through increasing concentration of carbon dioxide and other gases which absorb radiation is compelling attention to reducing fuel consumption. That associated with buildings in the UK accounts for nearly 50% of emissions.

The current technology for reducing fuel consumption in both new and old houses comprises mainly:

a) Reduction of heat loss by air sealing of holes in the building envelope, thermal. insulation of walls and roofs, and double glazing.

b) Control of periods of heating and temperatures by time-switches and thermostats.

c) more efficient energy conversion, as by the use of condensing boilers.

Little progress is being made in energy reduction by these techniques, partly because there is little incentive to save energy at present fuel prices, but also because they offer only limited savings, and are not cost effective. They are laborious and the necessary expertise and skills are very short in the UK building industry. Upgrading 23 million UK houses with these techniques would require many decades.

Moreover, misguided air sealing and intermittent heating cause condensation, mould, damp bedding and asthma, which has impelled most housing associations to spend typically E15000 per house on extensive refurbishment including full heating. But full heating is likely to increase energy consumption, and may still not prevent condensation, since removal of moisture is seldom adequately managed. Control of condensation by increased heating levels is not a viable solution when the imperative is to reduce fuel consumption.

The present invention is intended to address more directly the primary objects of heating buildings which are 1. to keep occupants thermally comfortable when and where needed.

2. to keep the building dry.

A different regime is intended, of continuous combined heating and ventilation of just living room, kitchen and bathroom. Heat will escape from these rooms to give some warmth to other rooms, keeping internal surfaces warmer and providing better comfort. Using exhaust air as input to a heat pump allows a more generous rate of ventilation without increasing heat losses, thus maintaining a healthier drying regime, which also improves the insulation value of the existing structure.

The two major routes for heat loss through glazing and ventilation, which are conventionally inadequately controlled, are reduced by a new type of insulating. window shutter, fresh air down flow over the Windows, and heat recovery with a small heat pump, which can provide probably 80% of the seasons heat demand, at higher efficiency than a condensing boiler.

Such shutters and fresh air down flow make utilisation of solar energy more practical in cloudy North European and similar chmates, where otherwise heat losses through large areas of glazing can be greater than heat gains, and its cost and complexity makes transparent insulation scarcely cost effective.

Essential technical features The present invention comprises many elements, each contributing to energy economy and which can be used in isolation, but together form a coherent system to provide at least an essential minimum of heating and ventilation while consuming relatively little energy.

1. A flow of fresh air through the building is induced by extracting stale air from bathroom and either corridor or upper landing ceiling, where stale moist air fingers before it re-circulates. Air extracted from these locations is likely to have a high concentration of contaminants, so reducing the necessary rate of ventilation. Further energy savings are made by enabling the bathroom to serve as a drying room, avoiding consumption of electricity in dryers.

2. Fresh air is admitted through adjustable apertures at the heads of windows and constrained to flow downwards across substantially the whole width of glazing. Being colder and denser than room air it will tend to sink naturally and turbulently, but the air may be induced to form a streamline flow separated from the glass or cling to the window surface by the Coanda effect. The air flow may be induced by extracton elsewhere in the building or by suitable fans near the window heads. The failing curtain of cold fresh air will tend to distance the warmer room air from the inner surface of the glass and thus reduce the otherwise substantial rate of heat loss from warm air to glazing. Any warmer room air which mixes with the incoming cold air is carried back into the room.

3. Other holes in the building envelope including open flues should be sealed. With a negative pressure in the building induced by the exhaust fan, air will tend to enter through any remaining unsealed holes, reducing the usual loss of heat as warm air by exfiltration through such holes.

4. Thermally insulating shutters, arranged to close in an upwards direction are fitted internally to the windows and closely to the adjacent structure, such as to enclose a well or void between the shutter system and window, but open at its upper boundary. In cold weather cold air fills such a well, cooled by its proximity to the cold glazing and denser than the room air, which will prevent the convection of room air into such well. The thermal insulation value of the shutters is thus effective up to the height to which they are closed, unlike other known configurations. The average thermal insulation value of such shutters, assuming reasonable opening regimes is calculated to be superior to sophisticated multiple glazing and -transparent insulation systems, thus greatly reducing heat losses and avoiding the cold sink effect of even double glazed windows.

5. The outer surface of the shutter is normally absorbent to solar radiation which is sufficient on south facing elevations in daytime usually to warm the adjacent air sufficiently to convect out of the well into the room. Slightly warmed air is displaced into the room by the colder air flowing down the inner window surfaces. Such a shutter system thus forms a valve for passive solar collection.. Moreover single glazing in narrow frames can transmit neady 50% more solar energy than double glazing. Such shutters plus single glazing can thus form highly effective yet inexpensive passive solar collecting fenestration.

6. Such shutters are also useful as shades against discomfort from direct solar radiation. They may also be fitted with reflecting outer surfaces to reduce solar gain to the building. And room air may be allowed to convect downwards in the void by providing a gap at the bottom to assist in dissipating heat gains from computers etc. on elevations shaded from solar gain. Such facilities can all assist in minimising need for air conditioning and energy consumption.

7. Heaters are fitted beneath windows, whether or not fitted with shutters, to heat the room to the required comfort level. It is good practice to locate heaters beneath windows, to counter the convective cold down draught of room air cooled by 2 the window surface, and to compensate for radiant heat loss to the cold window surface. In the present system the heater also warms the incoming cold air flowing down the window. The heater is preferably a panel which emits partly radiant heat. It may be a low temperature electrically heater panel.

8, Preferably the heater should be a water filled panel incorporated into the shutter system such that it can serve not only to heat the room, but also when space heating is not needed, to collect solar radiation to heat domestic hot water, by raising the outer shutter. To provide adequate heat output from relatively low temperature water from a heat pump, such panel should be larger than in typical practice with radiators served by a gas boiler.

9. The source of warm water to provide space heating through such panel is preferably a heat pump which recovers heat from outgoing stale air extracted as in I from bathroom or landing ceiling. Most advantageously, this delivers warm water to a large tank serving as a heat store and buffer, to accumulate heat on low electricity night tariffs to be drawn on as needed to maintain desired temperatures.

10. Such a heat pump is sized according to the space heating requirement, rather than to recover heat from outgoing stale air at a ventilation rate normally considered adequate. While the external air temperature is above the temperature of the exhaust air chilled by the heat pump, increasing the rate of ventilation makes more renewable energy available from the external air, with a commensurately sized heat pump. A higher rate of ventilation is desirable that that obtained in air sealed houses, or provided by typical domestic heat exchangers, to control indoor pollution, condensation, and asthma. Such system is particularly useful in buildings which are difficult to air seal, to minimise the loss of heat by exfiltration, and utilise infiltrating air as a heat source.

11. The exhaust duct from the heat pump is preferably vertically upwards, such that in less cold weather, when solar heat gains provide adequate heating, the heat pump and fans may be switched off, ventilation being maintained by the stack effect of buoyant warm air in the house relative to colder air outside. In warmer weather, buoyancy diminishes, and windows must then be opened to ensure adequate ventilation.

Example

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which figure 1 shows a vertical cross section of a bungalow.

An air to water heat pump 1 extracts stale air at ceiling level 2 in the corridor and from the bathroom at 15. The air is cooled and rejected to the exterior via a vertical duct 3 through the roof.

The heat recovered from outgoing air by the heat pump is used to heat water, which is circulated via piping 4 to a large storage tank 5 and to hot water radiators in living room 6 and in the kitchen, not shown.

Inward of the full height glazing 7 on the south elevation is a pair of vertically sliding shutters 8 and 9, between which is the radiator 6- Gaps are provided at top and bottom to allow warm air 10 to convect upwards from the radiator space to heat the room.

On a cold overcast day, the void 14 between shutter 8 and glazing 7 contains cold dense still air, preventing warm room air convecting into such void.

At night the shutter 9 is raised to the level of the window head 11, exposing the body of the radiator to the room. Another shutter at 11 can be lowered to close substantially the entire window opening.

In warm weather, the outer shutter 8 may be raised to allow the radiator to collect incident solar heat to heat domestic hot water, with suitable plumbing arrangement.

At the window head 11 are apertures 12 in the window frame, and an adjustable baffle extending the width of the window which constrains incoming fresh air to flow down the window surface and eventually mix with warm air convecting from the radiator.

Figures Figure I - Cross section of bungalow with full length south facing window, showing fresh air down flow, insulating shutters and heat pump extracting air from corridor.

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Claims (5)

Energy Saving in Buildings Claims

1. A system for reducing heat losses and passively collecting solar heat gain through glazing whereby incoming external air to ventilate a building is admitted at the head of said glazing and constrained to flow downwards over its internal surface, together with a system of insulating panels fitting closely to the surrounding structure such as to contain cold air in the well formed between such insulating panels and glazing, such cold air being displaced and replenished by said downwards flow of incoming external air.

2. A system as claimed in claim 1 where one insulating panel is fitted outwardly and one inwardly of a container filled with water or other heat absorbing material, such that the outer panel may be raised to expose one face of the container to collect radiant solar heat, or the inner panel may be raised to expose the other face to heat the room.

3. A system as claimed in claims I and 2 together with a system for extracting air from the building and cooling it to below external temperature with a heat pump and using the net heat gain to heat water or other fluid to circulate through the container in claim 2 towards heating the room when the inner shutter is raised.

4. A system as claimed in claims 1, 2 and 3 in which water or fluid can be circulated through the container in Claim 2 with the outer panel raised, such that when not all the passive solar gain is required to heat that room the solar heat can be absorbed through the container to be utilised towards heating domestic hot water.

5. A system substantially as herein described and illustrated in the accompanying drawing.