Britain had its hottest June day ever for the third time in a row today, with highs of nearly 37C - but those living in new-builds have claimed to feel the heat even more.New build properties continue to pop up in the UK, attracting prospective buyers who are keen to secure chain-free, low-maintenance living.According to the Britons who have made the purchase, however, there's a downside - feeling like you're in the 'Sahara Desert' during the summer months.Unlike older homes, new developments tend to be highly energy-efficient, meaning heavy insulation, unshaded windows to maximise natural light, airtight construction - and so, 'boiling' temperatures in the heatwave.Social media users have taken to TikTok to complain about their living conditions, with one, Rosie Mantalbano, likening her house to the world's largest hot desert.Taking to TikTok while sitting on the sofa in her bikini, Rosie said: 'Can we talk about why newbuild houses in the UK retain heat so well? It's 32C outside, and my house feels like it's sponsored by the Sahara Desert.'I've had the windows open since 7am this morning, I've had the curtains shut all day, nothing is working. The walls are literally hot to the touch.'Don't even get me started about the nighttime, my pillows are hot, my duvet is hot, my mattress is boiling. This morning I woke up, and I felt medium-rare. It was horrible. The UK continues to experience its hottest ever June weather - and those living in new builds, including Stan Milsom (pictured) claim the temperatures inside their home are 'horrible''I feel like British houses, especially new buildings, were built for the rainy and cold weather, not this weather. Someone send help.'She's not the only one. Abigail Jade Brown likened her house to 'hell', saying: 'Trying to survive this heatwave in a new building. I'm in hell. I feel the thunderstorm only made it hotter.'Elsewhere, TikTok user @ourcastletonhome registered a temperature of 29.5C inside their home, writing: 'POV: You live in a new building during a UK heatwave,' alongside a clip of the thermometer.Stan Milsom, meanwhile, told his followers that he's considering installing air conditioning in his new build to make the conditions bearable.The TikTok user said: 'If you're thinking about buying a new build, be prepared for extreme heat.'I'm actually sweating. Normally in this house, it is hotter inside than it is outside. It's actually unbearable. I used to do air conditioning for a living so I'm planning on putting a unit in here soon.'According to the Mirror, the Climate Change Committee said in May that UK homes are now 'built for a climate that no longer exists' in a statement that also called for nationwide air conditioning.Dr Ben Roberts, senior lecturer in healthy buildings at Loughborough University, told the Daily Mail: 'Traditionally we've been quite a cold country so we've been looking at keeping our houses warm in winter. Abigail Jade Brown (pictured) told her TikTok followers said her 'house feels like it's sponsored by the Sahara Desert' Rose Montalbano (pictured) likened her new built to the Sahara Desert - and said nighttime is the hottest'It's only since 2022 that we've had building regulations which have started to look at keeping our homes cool in summer. So, we've got a bit of catching up to do.'This raises the question of whether blinds should be kept down, windows left open, and fans kept on. But the answers can vary depending on the type of property you live in.Top-floor flats, for example, tend to become hotter as heat rises, while homes with larger windows can also warm up rapidly in direct sunlight and shaded properties may be far cooler.As a general rule of thumb, however, Dr Roberts advises that most people should always put their blinds down during the day.He said: 'If they are light in colour, or some kind of reflective metal, then it is worthwhile keeping your internal blinds or curtains closed during the day to stop the sun's heat coming in because it will reflect some of that heat back out.'For ventilation, the best approach is to open windows on opposite sides of a home during the coolest parts of the day, typically overnight or in the early morning, when temperatures are at their lowest.Creating airflow through the home in this way allows cooler air to circulate more effectively than opening windows on just one side of the property.Dr Roberts said: 'Whenever it's warmer outside than in, opening your windows just lets that hot air in. The general advice is that, during the peak of the day during heatwaves, it's almost always that it's going to be hotter outside than in - so that's when you should be keeping your windows closed.'Then at night, when it's likely to be cooler outside than in, that's when you should open your windows if it's safe to do so.'Obviously for a lot of people, especially if they're living in ground floor flats or noisy polluted areas, there's a variety of reasons why people might not want to open their windows. But the general advice is open your windows at night close them during the day during heatwaves.'If a home has only one window, a fan positioned nearby can help move cooler outside air further into the room and improve flow throughout the property.Leaving a fan on during the day, however, is not advised by experts.Dr Roberts says: 'There's no benefit to having a fan on if you're not in the home because all the fan is doing is it's moving the air - it's not changing the temperature of the air.'Unless you're there to receive that air movement and feel that air movement across your skin, and to have that additional sweat evaporation that the fan creates, it's doing nothing.'It comes as the Met Office said a temperature of 36.9C was recorded at Wattisham in Suffolk - one day after a new June record of 36.7C was set yesterday in Merryfield, Somerset.That came after another new record on Wednesday of 36.1C in Gosport, Hampshire; which itself beat a longstanding June high of 35.6C dating back to summer 1976.Today was also the UK's seventh hottest day ever, above a 36.7C record set in 1911 in Northamptonshire, which had stood as the country's hottest day for nearly 80 years.Today is also a record-breaking third consecutive day of red extreme heat warnings in the South East. A wider amber warning for the East and Midlands was also in place.London and Manchester could reach 36C today, with Belfast and Cardiff at 26C. This follows another 'tropical night' when temperatures failed to fall below 20C - with the highest overnight low in Herstmonceux, West Sussex, dropping to only 22.7C.The Government's UK Health Security Agency (UKHSA) has now extended its amber alert heat warnings until Sunday morning for the whole of England, warning of a 'rise in deaths, particularly among those aged 65 and over or with health conditions'.