The UK domestic solid-wall housing stock is a particular focus by reason of its considerable space-heating energy consumption than in any other sector because these are so far anticipated to be hard-to-heat. Existing UK solid-wall houses, which have both heritage values and historic fabric, are being improved but yet they tend to have preventable heat loss through windows. This paper takes a comparative analysis approach to envisage space-heating supply required for achieving thermal comfort temperatures and attainable solar energy gains to households with the retrofit of the thermal transmittance (U-value) of a new composite edge-sealed triple vacuum glazing i.e. 0.33 Wm-2K-1. 3D dynamic thermal models (timely regimes of heating, occupancy, ventilation and internal heat gains) of an externally-insulated solid-wall detached house with a range of existing glazing types along with triple vacuum glazing with frame areas are modelled. The predictions of varying window-to-wall ratios on space-heating energy and solar energy gains for winter months are analysed. The results have shown by increasing WWR from 5% to 59%, the winter months space-heating energy supply to the solid-wall detached house slightly decreases with triple vacuum glazed windows whilst a gradual rise was noticed with single glazed windows. A small increase in solar gains, i.e. 5.6 kWh, was predicted for a room with a triple vacuum glazed window compared to a triple glazed air filled window. However, with similar increment to WWR, the house achieved higher solar gains with single glazed windows. The notable winter and annual space-heating energy savings of 14.58% (EUR 49.2) and 15.31% (EUR 105.4), respectively, were obtained with a solid-wall detached house retrofitted with triple vacuum glazed windows compared to single glazed windows. In the overall fabric heat loss, the heat loss calculations show a prominent reduction from 12.92% to 2.69% when replacing single glazed windows to triple vacuum glazed windows. However, the space-heating energy cost savings can be more significant when the solid-wall insulation is improved to 2010 UK building regulations. Simulated results show a negligible space-heating and cost savings with a house of double argon glazed windows compared to double glazed air filled windows. Solar gains do contribute in reducing the space-heating load but during summer months it could cause overheating and may be inconvenient to households and cooling is essential in such circumstances. Thus, the triple vacuum glazing, if manufactured at the mass production level with cost-effective airtight sealing materials and improved fabrication methods, is a great opportunity in reducing building energy consumption and has a potential to increase window-to-wall area ratios without a risk of overheating during summer months.