Mike McEvoy

Test cell analysis of the use of a supply air window as a passive solar component

Abstract A series of experiments was conducted to determine the performance characteristic of a ‘double’ window used to pre-heat background room ventilation. A theoretical model of heat exchange conditions within the window was compared with results from a test cell. The test cell was used in different modes, firstly free-ventilated with the service room window and interconnecting duct to the cell left open, and then with forced ventilation at a consistent velocity to analyse the relative extent of direct solar and ventilation heat gain. A subsidiary study sought to determine the frequency of positive and negative air flow through trickle vents under real house conditions, this was compared with glass temperatures from the test cell measurements to assess the risk of condensation forming within the window. By reference to recent work on ventilated PV systems it was possible to derive a method of relating the U value and Solar Heat Gain Coefficient within the window cavity to a range of boundary conditions.

Test cell evaluation of supply air windows to characterise their optimum performance and its verification by the use of modelling techniques

Abstract A supply air window is a device that by using the space between inner and outer sashes as an air path enables ventilation air in winter to be pre-heated before it enters a room. For optimum results it is necessary to maximise the window’s capability as a heat reclaim device (by entraining into the air flow heat that would otherwise escape from the room) and its ability to absorb radiant energy from the sun. The principal requirements for achieving best performance include defining appropriate dimensional characteristics for the window, and the correct location of a low emissivity (low-E) coating within the glazing assembly. To determine these aspects tests were carried out using a PASSYS test cell. The performance of the window was monitored relative to climate conditions measured at an adjacent weather station. A simulation model of the test cell was built and comparison was made of the actual performance with forecast figures.

Architecture and construction in steel

Preface. Contributors. Introduction. Part 1: History of iron and steel construction. The nineteenth century. The twentieth century. Part 2: Materials. Properties of steel. Structural steel components for buildings. Steel sheet and strip. Stainless and related steels. Nature of corrosion. Anti-corrosion measures. Fire protection. Part 3: Principles of steel framing. The architecture of steel. Basic theory of framing. Multiple bay single-storey buildings. Floor framing and services above and below floors. Multi-storey frames. Tall structures. Composite floors and structures. Transfer structures. Foundation structures. Atria. Tensile structures. Part 4: Steel construction. Structural connections for steel work. Fabrication and erection. Tolerances and movements in building frames. Insertion and strengthening of steel frames and upgrading facades. Part 5: Secondary steel elements. Principles of cladding. Heavy and lightweight cladding. Window walls and rain screen facades. Decking and built up roofing. Fastenings. Metal stud work and lath. Metal windows and louvres, cills and lintels. Metal door frames, screens and security. Staircases and balustrades. Gutters, downpipes and overflows. Decorative iron and steel. Part 6: Outstanding contemporary steel architecture. The last 25 years. Structural steel design awards. Futures. Appendices: Relevant codes, standards and general publications. Advisory services for the steel construction industry. Index of architects. Index of buildings. Subject index.

A programme of testing to evaluate a passive approach to whole‐house ventilation

Purpose – The purpose of this paper is to describe a programme of research into an innovative approach to whole‐house ventilation with heat reclaim. In order to save energy, houses are now required to be constructed to a high level of air tightness. This poses potential problems of indoor air quality, condensation and mould growth, with implications for human health. Adequate and controlled ventilation is a necessity, and in Europe the adoption of mechanical systems incorporating heat reclaim has become the preferred technology. The relatively mild climate of the UK undermines the efficiency of these fan‐driven solutions. The programme of research has been to test the viability of an engineered system of natural ventilation for use in temperate regions.Design/methodology/approach – The system works by the combination of “supply air” windows and passive stacks. The windows have an air path for incoming ventilation that passes between panes of glass, the pressure drop across the windows to induce the air fl...

Comparison of the Performance of a Whole House Low Energy Ventilation System in Contrasting European Climatic Regions

An experimental ‘whole house low energy ventilation system’ has been installed and tested in dwellings in Denmark and Poland. Both sites have adjacent houses of identical plan layout, which have been used as a control for the experimental dwellings. A weather station was installed adjacent to each site, and each of the dwellings, test and control, has been extensively monitored to measure indoor airflow and comfort conditions, and the amount of energy being supplied for heating in winter. The design of the systems was established by computer fluid dynamic (CFD) analysis and by a dynamic simulation using ESP-r. The low U-values that can be achieved by ‘air supply’ windows, suggested by previous tests and simulations, have been confirmed by the monitored results. Similarly the levels of preheat to ventilation air achieved by the windows have reached the percentages expected from the simulation models. Practical application: This study is part of an ongoing investigation into the use of an innovative technology for whole house ventilation. Since this is the direction of the forthcoming revision to the UK Building Regulations it has obvious implications for practice.

A Simplified Method for Referring the Energy and Overheating Performance of Window Design

This paper describes a simplified dynamic thermal model which simulates the energy and overheating performance of windows. To calculate artificial energy use within a room, the model employs the average illuminance method, which takes into account the daylight energy impacting upon the room by the use of hourly climate data. This tool describes the main thermal performance (heating, cooling and overheating risk) resulting from proposed a design of window. The inputs are fewer and simpler than required by complicated building simulation programmes. The method is suitable for the use of architects and engineers at the strategic phase of design, when little data is available.

Derivation of a Theoretical Model to Explain the Functioning of a Window as a Pre-Heat Ventilation Device and its Verification using Physical Models

Abstract ‘Supply air’ windows are designed with an air gap between the inner panes of glass that is used as the incoming air path for room ventilation; air is pre-warmed within the window and thereby avoids the sensation of draughts. A series of tests, verified by model simulations, were carried out to determine those aspects of the window’s specification that govern the extent to which air is pre-warmed by the windows before entering rooms. The first was a laboratory experiment investigating the influence that the width of gap between the glass panes had on the pre-heating of the airflow, the results from which were simulated using an algebraic model based on fluid dynamics principles. The following experiments were carried out in test cells analysing the influence of the location of a low emissivity coating within alternative glazing assemblies, the relationship between pre-heat temperature and ambient temperature, and its variation with ventilation rate. The later stages were modelled by the use of the Computational Fluid Dynamics program FLOvent. The outputs of these experiments and simulations has enabled a clearer understanding of the physical processes at work, and the development of simulations that accurately predict the window’s performance as a pre-heat device.

Description of a Programme of Testing and Simulation to Establish the Determinants of the Effective U-Value of a "Supply Air" Window

The ‘supply air’ window is in essence a modified Scandinavian ‘double’ window having outer and inner sashes with a gap between them forming a route for the ingress of ventilation air. When operating under optimum flow conditions, the air stream is laminar, so that a high proportion of the heat escaping from the room is entrained in the air path and returned to the room as pre-heated ventilation air. In this way very low U-values can be achieved and a proportion of the ventilation heat load is met by the preheating of the incoming air. A series of tests have been carried out using a laboratory test rig and test cells to determine the optimum specification for the window and its glazing in order to achieve the best performance in terms of insulation, indoor air quality and comfort. The results presented here investigate the factors influencing the U-values that can be achieved. The data from experiments has been compared with model simulations preparatory to testing under real house conditions.